Category Archives: numismatics

Gallery

Crusaders and money, seen in a different way

This gallery contains 10 photos.

This strategy I have adopted of putting the current content up top and the backlog below is getting somewhat top-heavy, but there is just one more thing to announce, and then I expect actually to start letting some of these … Continue reading

A prophetless coinage

I stubbed this post quite soon after starting at the Barber Institute with no intent more serious than to post a picture of a marvellous coin and enthuse about it. And I hope you can see why!

Gold solidus of Emperor Heraclius and his two sons, struck in Constantinople between 638 and 641, Barber Institute of Fine Arts B2912

Gold solidus of Emperor Heraclius and his two sons, struck in Constantinople between 638 and 641, Barber Institute of Fine Arts B2912

This is, as the caption says, a solidus of Heraclius with his two sons, whom we usually know as Heraclius Constantine and Heraclonas but whose given names were both Constantine, and the former of whom subsequently reigned briefly as Constantine III (641). There is lots to say about this coin type, which was novel in many ways: there is for example no legend identifying the emperors, only a monogram of Heraclius’s name on the reverse to the left of the cross, which will be important in a moment; it is making a strong point because the Church opposed the legitimacy of Heraclonas, who was Heraclius’s son by Empress Martina who was also Heraclius’s niece; and one could go on. But I mainly wanted to post it because they look so much like a poster for a superhero movie; one can almost see the cloaks billowing in the studio wind. (My original title for the post was Emperors Assemble…) I am not the only person who’s put these online, but who cares? But then very recently, while looking up stuff for a different project, I found a web-page discussing an Arabic imitation of this coin type which had a couple of things badly wrong with it, and a bigger point emerged.

Gold dinar struck in Syria between 639 and 705, Barber Institute of Fine Arts A-B30.

Gold dinar struck by an unknown authority in Syria between, well, who knows? 639 and 705 would be probably-safe outside guesses. Barber Institute of Fine Arts A-B30.

You can immediately see both the similarities and differences. The Latin legend is replaced by Arabic, and the Arabic reads, for those who can, ‘bism allah la illah allah wahda-hu mohammed rasul allah’, ‘In the name of God, there is no god but God, Muhammad is the prophet of God’. The monogram goes, being replaced perhaps by the beginning of the Bism Allah in Latin letters. All crosses are all replaced by pellets, so that the three figures now look oddly as if they’re holding walking canes and the cross-on-steps becomes a pole-on-steps. But it’s plainly the same type underneath it, I’m sure you’ll agree.

All of this is something that can be seen on copper coins of similar types which are presumed to come from the same period, normally guessed at between the 670s and 695 or so, in which latter year Caliph ‘Abd al-Malik seems to have begun a reform of the disparate coinages of his realm which would unite them into one system of coins with no pictures, only script, running over Arabia and Persia alike. Before then, however, and in some places also after then, coins like this that echoed, imitated and adapted previous types, both Byzantine and Persian, had been the working currency. Few of those were gold, however, and few of these ones are known; the web article I linked to above says that all the known ones are in the British Museum. Well, one of them is in the Barber Institute of Fine Arts—in fact, it and I have both spent much of the week in the School of Chemistry with an XRF machine, but let that pass—and that is the first mistake I wanted to correct.

The second, though, is that the article suggests, following a Flickr site called Taboo Numismatics to which it links, that the Arab-Byzantine type (as these adaptive coinages are canonically called) actually depicts the Prophet Muhammad. Now, one can see the argument: there is a bearded figure on it and the reverse legend names the Prophet, albeit in terms that might equally just be a profession of faith. Still, the name is there and the picture is there, and the fact that they’re not on the same face is a problem but one that also exists for the Heraclius coin.

There is also the problem that Islam is supposed to abhor images of people, of course, and as we know of recent years to be especially keen that the Prophet not be depicted. This has not always been so, however, and indeed the point of the first site that I linked to is explicitly that, that many medieval images of Muhammad from Islamic contexts are known. There are also coins for which this case would be much stronger, which take a new image of a standing figure in a headdress, carrying a broad sword, and place the legend ‘Muhammad rasul Allah’ around him. The type also exists naming ‘Abd al-Malik, and the ‘Muhammad’ version of it seems only to have been struck in Palestine, but we don’t know how they relate; it’s usual to assume that ‘Abd al-Malik introduced the design and that for some reason Palestine only struck it anonymously, but it seems equally possible to me that Palestine did actually strike a coin showing the Prophet and that ‘Abd al-Malik borrowed the design for his halfway-house pre-reform coinage. The Barber does have some of these coins, but I’m chary of putting images of them on the web right now: you can see one that was sold in 2013 here, and here’s one of the ‘Abd al-Malik ones.

Copper fals of 'Abd al-Malik, Commander of the Faithful, struck at Manbij between 680 and 696, Barber Institute of Fine Arts A-B36

Copper fals of ‘Abd al-Malik, Commander of the Faithful, struck at Manbij between 680 and 696, Barber Institute of Fine Arts A-B36

If there is to be a search for early Islamic coins showing Muhammad, therefore, it’s with the ‘Standing Caliph’ types of Palestine that it must start. The Three Standing Figures gold dinars won’t really work for it. Yes, there is the legend, but there are also many points against. In the first place, the portraiture is so exact a copy of the coins of Heraclius, right down to the barbs of the moustache, that it is clear that one of those coins was before the engraver. They would, indeed, have been fairly frequent among gold coins in the area and so the resemblance would have been noticeable more widely. What message could this be meant to send if that coin were showing Muhammad? That he had somehow been Heraclius? It seems unlikely. But even then, there are three figures: who are the others? The site I started with makes a spirited attempt to explain them as Abu Bakr, the first Caliph, at Heraclius’s right and Aisha, Muhammad’s wife, at his left, but this also won’t really work; that site has the advantage (for these purposes) of a fairly poor image that allows him to maintain that the right-most figure is veiled, but our own won’t easily allow that. It seems very much simpler to say: they’re not supposed to be anyone, but they are supposed to look like what the figures on those gold coins the people of the area knew looked like, with suitable adaptations to point out that something new was in fact going on. There is gold of the Standing Caliph type, too, naming ‘Abd al-Malik, so this presumably didn’t last very long, but in any case. I’m pretty sure that what I’ve just put online is not a picture of Muhammad!


The most accessible study of the Arab-Byzantine coinage is Clive Foss, Arab-Byzantine Coins: an introduction, with a catalogue of he Dumbarton Oaks Collection, Dumbarton Oaks Publications 12 (Washington DC 2008), which does discuss the Muhammad problem. Note that Tony Goodwin, “The Arab-Byzantine coinage of jund Filastin – a potential historical source” in Byzantine and Modern Greek Studies Vol. 28 (Leeds 2004), pp. 1-12, also argues that the Standing Caliph coinage of Palestine is earlier than ‘Abd al-Malik’s. To Tony Goodwin also goes the honour of publishing the Barber’s dinar, along with some others from this part of the collection, as “Some Interesting Arab-Byzantine Coins from the Barber Institute Collection” in Numismatic Circular Vol. 111 no. 4 (London 2003), pp. 196-198. It remains for me and my collaborators to get any more of them out there…

Gallery

The Empress, her Son, her General and his Heir

This gallery contains 15 photos.

Another day, another upload of Barber Institute coins to the web! This one is only small, 27 coins, and these comprise the coins of the notorious Empress Eirini, with her son Constantine VI (780-797) and then without (797-802), and those … Continue reading

Faith and Fortune is back, in Exeter

Masthead of exhibition Faith and Fortune: visualising the divine in Byzantine and Islamic Coinage, at the Barber Institute of Fine Arts, 8 November 2013 to 30 November 2014

Masthead of exhibition Faith and Fortune: visualising the divine in Byzantine and Islamic Coinage, now on show again, at the Street Gallery, Institute of Arab and Islamic Studies, University of Exeter

If you remember me mentioning Faith and Fortune: visualising the divine on Byzantine and early Islamic coinage, the rather excellent coin exhibition at the Barber Institute of Fine Arts which preceded my current one, and thought it sounded fun but did not in fact manage to go to it, you may be pleased to know that there is now a second chance! By a happy series of coincidences the fine people in charge of the Street Gallery at the Institute of Arab and Islamic Studies at the University of Exeter got to hear about it and decided they would like to host it, and so in April we packed the boards up and sent them down with supporting materials and one of the original curators, Dr Rebecca Darley, in tow to give an introductory lecture. It has been open since 25th May (sorry) and will be until 19th December 2015, so there is plenty of time to go and see it still! I present the exhibition information:

Faith and Fortune is the first exhibition in several years that draws exclusively from the in-house collections of the Barber Institute of Fine Arts. The principal chronological focus of the exhibition spans the years A.D. 300-750 but includes later 13th-century Turkmen material. The exhibition has been the focus of a presentation at the British Museum and has received positive reviews from specialists in medieval history, the Middle East and numismatics. It focuses on these particular themes and the current scholarly and research interest in Late Antiquity. The over-arching theme of the exhibition concentrates on the use of Late Antique coinage as a platform for the promotion of the respective political and religious ideals of the Byzantine, Umayyad and Sasanian Empires. This focus serves as a springboard for the exhibition to explore divergent attitudes among Byzantine, Sasanian and early Islamic societies regarding the representation of divine figures or religious subjects. The exhibition is curated by Rebecca Darley (4th-7th century Byzantine and imitation coinage) and Daniel Reynolds (7th-8th century Arab-Byzantine and early Islamic coinage) and the expertise of the Coin Collections Assistants Maria Vrij (7th-9th century Byzantine coinage and iconography) and Ali Miynat (Turkmen coinage).

Display of the exhibition Faith and Fortune: visualising the divine on Byzantine and early Islamic Coinage, at the Street Gallery, Institute of Arab and Islamic Studies, University of Exeter

The display in situ at the Street Gallery

This image was a bit peculiar to receive, because I’ve been there: two of the conferences I’ve been to at Exeter have been held in the Institute of Arab and Islamic Studies and I clearly remember not being able to afford to buy Richard Hitchcock’s books in that gallery space. Nonetheless, it is a good space for actual displays too! You will observe that there are no display cases, so we were not able to send the actual coins along with the boards; instead they have been replaced with life-size photographic reproductions that get the points across nearly as well. I must also acknowledge the help of Rebecca Darley of the Bilderfahrzeuge Project at the Warburg Institute, University of London, Evelina Kuvykovaite of the University of Warwick and Jane Clark and the team at the Street Gallery for making it all so easy for us collectively to set this up; it was remarkably easy to do, and hopefully worth it for many visitors!

Link

An array of interesting links

I tend to store up interesting links against a day when I have no content to post, but the backlog situation has meant that not only does that never occur any more but that the links themselves get very old. I thought it was about time to clear some out! I had so many that categories seem necessary, even. So let me humbly suggest that you may wish to click to learn more about the following:


    Things from out of the ground

    A Celtic disc brooch looted by Vikings and now in the British Museum

    A Celtic disc brooch looted by Vikings and now in the British Museum, see below

  1. In no particular order, a previously-undiscovered Viking fortress, at Vallø in Denmark, located in mid-2014 by laser imaging and ground-penetrating radar;
  2. I have been known, in my cynical past, to say that the best way to hide an archæological discovery you wish to keep secret is to give it to the British Museum, due to their cataloguing backlog, but I was not wholly serious obviously, whereas this is a bit ridiculous (but has that brooch in it);
  3. further stuff has also been found, as is now de rigeur for all credible archæology in the UK, under a car-park, in Haddenham in Cambridgeshire where they hit what seems to have been a small sixth-century Anglo-Saxon cemetery during development work in February 2014;
  4. some eighth- to -tenth-century bodies found stuffed in a well Entrains-sur-Nohain in Burgundy provoke the writer of that post to several equally hypothetical Carolingian-history explanations
  5. an Iron Age hillfort at Broxmouth in East Lothian, Scotaland (just), has revealed what seems to be evidence of fifth-century BC steel-making;
  6. and there has been an array of hoards discovered that need their own subsection:
    A silver lidded vessel of Carolingian date recovered in a hoard from Dumfries in 2014

    A silver lidded vessel of Carolingian date recovered in a hoard from Dumfries described below

    1. a hoard of Viking silver loot, including what was once a really nice Carolingian lidded ewer or similar, found near Dumfries in south-west Scotland in late 2014;
    2. “one of the largest Roman coin hoards ever discovered in Britain”, 22,000 or so third-century coins found in Devon in November 2013 but only breaking into the news in September last year; I think Georgia Michael told me about this one so hat tip to her;
    3. and although 5,000 coins suddenly seems like not so big a deal, nonetheless, for the Anglo-Saxon period it is; I’m pretty sure this find nearly doubles the amount of King Cnut’s coinage known to exist in the UK, for example, and this one I definitely do owe to Georgia so off that hat comes once again;
    4. Posed photograph of some gold dinars from a hoard found off the coast of Israal

      I would not let someone do this with a gold find even before it had been catalogued, myself, but I am not the Israel Antiquities Authority, in whose care this hoard of Fatimid gold dinars ended up (see left)

    5. and two thousand is hardly trying, but firstly these ones were gold and secondly they were off the coast of Israel, dating to the reigns of the tenth- and eleventh-century Fatimid caliphs Al-Ḥākim and Al-Ẓāhir, and possibly coming from a sunken tax shipment, which I bet has caused a lot more diving since the news came out and which news I owe, once more, to Georgia Michael, who must have got the idea that I like coins or something…

    Things afoot in the research world (including those parts of it that blog)

  7. A new(-ish) project running out of Oxford to map all the various hillforts of the British Isles, presumably including that of Broxmouth above…
  8. … out of which project came the following endeavours from my native land, with lots to read if hillforts are of interest to you;
  9. a thorough and useful set of suggestions about what was wrong with the UK’s Research Excellence Framework exercise, not including its terrible name but with many other good points, from the self-appointed but persuasive Council for the Defence of British Universities (and here I owe a tip of the hat to Professor Naomi Standen);
  10. more light-heartedly, here is a reason for scribal errors that I had never considered, and still rather wish I hadn’t given some of the suggested remedies;
  11. a suggestion from a doctoral researcher at Sheffield that the current male fashion for extreme facial hair has medieval precedents, and plenty of modern ones too (a tip of the hat here to one of the Australian Medievalists);
  12. Things from out of the archive

    Fragments of a mid-seventh-century manuscript of the Qu'ran in the Mingana Collection, Cadbury Research Library, University of Birmingham

    Fragments of a mid-seventh-century manuscript of the Qu’ran in the Mingana Collection, Cadbury Research Library, University of Birmingham, see below

  13. Some extra fragments of illustration from the Catalan comital cartulary known as the Liber Feudorum Maior have been rediscovered!
  14. Following our theme of materials for the study of Anglo-Saxon England feared forever lost to scholarship, you may not necessarily be aware that after much deliberation about what to do with it, Professors Stephen Baxter and John Hudson have published the unfinished second volume of Patrick Wormald’s The Making of English Law on the Early English Laws website as Patrick Wormald, Papers Preparatory to the Making of English Law, vol. II, for which many people may be very grateful;
  15. the Vatican Library’s digitisation project has a new website and a much more searchable catalogue, though it does admittedly appear to be broken just now;
  16. and, to end with something at least that is very new and exciting, we have a lot of people coming to the Barber Institute just now because they have not read far enough down this story to realise that the very very early Qu’ran manuscript it describes is not yet on display here, but it is still extremely exciting!
Gallery

Byzantium before Byzantium

This gallery contains 4 photos.

I’m pleased to say that since about May my team and I at the Barber have been making steady progress in getting at least some of our coins onto the Internet, and this is another post to tell you about … Continue reading

A problem of concavity

Now that I am returned from all my conferences, I have a few very frantic months left as a numismatist before I demit that noble calling so as to return to medieval history of more traditional sorts. In fact, of course, I will not be leaving the coins completely behind me: almost the first thing I will be doing in my new rôle is to give a guest lecture back at the Barber Institute, as part of my own exhibition there, and then I’ll be going to the International Numismatic Congress in Taormina, and I should just be back from that in time to start teaching the aftermath of the end of Roman rule in the West. And in fact, even then, I shall have enough publication projects in hand what with All That Glitters and a couple of other things to do with the Barber’s collections that it may take a while for anyone to notice that coins are not, in fact, what I work on… In that spirit, therefore, here is something like an informal presentation of the problem my paper at Taormina will be addressing, which I do mainly so as to have a first go at posing the problem in text. Basically, my question is: why did Byzantine coins turn concave?

A tray full of pale gold and billon coins of Emperor Manuel I Komnenos (1143-1180) in the Barber Institute of Fine Arts, Barber Institute of Fine Arts B5704-B5735

A tray full of pale gold and billon coins of Emperor Manuel I Komnenos (1143-1180) in the Barber Institute of Fine Arts, all concave, Barber Institute of Fine Arts B5704-B5735

It is perfectly reasonable for your first reaction to this question to be “What?”, don’t worry. But this is a thing that happened: from the 1050s onwards, more or less the reign of Michael IV (1034-1041), Byzantine precious metal coinage began to be manufactured with a slight dish-shape that became more and more pronounced, and then spread to the lesser metals too. It also went badly downhill in metal quality, and by the reign of Emperor Alexios I Komnenos (1081-1118) the situation was so bad that despite the massive calls on his empire’s much-reduced resources he reset the coinage in the only way one really can in an international precious-metal economy, by accepting the degradation of the existing coins, reclassifying them and introducing a new, 80%-gold denomination, the hyperperon at the top of the tree.1 The old supposedly-gold nomismata became either electrum (gold-silver alloy) or billon (lightly-silvered copper) ‘trachies’, and this meant that the small change was also now concave, though there was also a flat bronze tetarteron that was used especially in what is now Greece.2 Anyway, I digress. The real question is, why adopt the dished design anyway?

A billon trachy of Emperor Alexios I Komnenos, struck at Constantinople in 1092-1118, Barber Institute of Fine Arts B5558

A billon trachy of Emperor Alexios I Komnenos, struck at Constantinople in 1092-1118, Barber Institute of Fine Arts B5558

One thing, and really one thing only is sure about this, which is that it was not an easy thing to do. In the first place, the designs on the dies with which the blank coins were struck were carved in such a way as to keep the design correctly proportioned: it looks straight even though it’s bent, something that becomes very evident when you try to photograph them in such a way that they face you but are still clearly concave. Scanning is better for this because the fall of light emphasises shadow, but with adequate lighting the concavity is quite often visually undetectable in conventional photography. So that was cunning artistry, and not least because the dies themselves, we are fairly sure, were made curved, rather than deforming flat coins by striking them.3 In fact, it seems likely that the flat blanks were first struck with blank dies to curve them, and then the resulting curved blanks were struck with two obverse dies, one for each side of the coin’s design, to ensure a good impression all over the coin’s surface.4 This means that the manufacturers were readier to triple the production process complexity than to make dies that fitted each other snugly, apparently, but we can mainly take from this: there must have been a point to all this, but what?

Electrum nomisma histamenon of Emperor Alexios I Komnenos, struck at Constantinople in 1081-1092, Barber Institute of Fine Arts B5224

Electrum nomisma histamenon of Emperor Alexios I Komnenos, struck at Constantinople in 1081-1092, Barber Institute of Fine Arts B5224

None of the existing ideas seem very satisfactory. They are, roughly:

  1. it made the coins stronger, preventing them snapping;
  2. it made the metal quality of the coins more evident, reassuring people that they were good;
  3. it made the coins stackable in a way that the relatively high-relief flat ones were not;
  4. it brought coins whose low standard had made them much bigger than the older solidi with which they were notionally interchangeable, because gold is denser than anything it might be replaced with, back down to a more acceptable width;
  5. it made the coins better to play tiddly-winks with.5

Now, don’t worry if you’re already laughing at this; I think it is fair to say that thinking about this problem has not been the highest achievement of numismatics as a discipline. But if you’re not quite seeing the problems here, let me set them out for you.

  1. The concavity may make the coins harder to bend, but it makes them far more prone to cracking, because the edges come out so thin, as you see below. And once a coin is cracked, it’s actually in much more danger of snapping; we take a lot of care not to drop these things, in case that fault line should just complete on impact. Yet the practice was maintained for long after that would have been apparent. So, no.
  2. Electrum aspron trachy of Emperor Manuel I Komnenos, struck at Constantinople in 1143-1180, Barber Institute of Fine Arts B5702

    Electrum aspron trachy of Emperor Manuel I Komnenos, struck at Constantinople in 1143-1180, Barber Institute of Fine Arts B5702, nothing a bit of solder wouldn’t fix! (I jest.)


    Billon aspron trachy of Emperor Manuel I Komnenos, struck at Constantinople in 1143-1180, Barber Institute of Fine Arts B5758

    Billon aspron trachy of Emperor Manuel I Komnenos, struck at Constantinople in 1143-1180, Barber Institute of Fine Arts B5758, probably beyond the soldering iron…

  3. The metal quality certainly is more evident, because of those same thin edges, but in that case it would be quite important to maintain that quality. Yet the concave coins went through just the same nosedive of purity again once reformed, and you’d think that even if making them flat again would have been some kind of admission of failure, at least it would have been unclear how badly you’d failed, whereas with the concave coins there’s no hope of concealment.
  4. They just don’t stack, seriously. The manufacture was not regular enough to guarantee anything but the most basic fit. And why on earth would this have been a desirable thing here, when even cultures that use money in strung-together multiples like Chinese cash are still flat? A much better way to do this would have been to cut the designs in lower relief, or just cut them deeper than the surrounding border, so that that became the point of contact between any two coin faces. I find this one actually a silly explanation, sorry.
  5. This seems to me to presuppose a point beyond which coins were just thought too big to use, one which is only obvious if you accept that this practice shows that the Byzantine Empire had passed it. But it had used bigger coins than this before and done nothing similar. So I see no reason to accept this kind of supposed cultural universal, but even if you do, one could have achieved the same result just by making the coins thicker, which would also make them stronger. It would make them harder to strike, in terms of force, but less fragile in manufacture, easier to cut dies for and anyway, brute force was not something any pre-modern state really lacked a supply of.6
  6. In so far as I’m going to take this seriously at all, why would you start with the gold for something that would ordinarily, surely, be played with low-value coins? And why on earth would the emperor care anyway? Still more why would any subsequent emperor not repeal this in the next reform?

So, we don’t have a good explanation. In Taormina I will try to propose one that is at least less bad, and that focuses more on the manufacturing process and its changed characteristics. I have a lot to read still, and I don’t want to give away my unique selling point as yet, although I’ve tried it in the classroom a few times by now, so for now I’ll go no further, but I hope I’ve at least intrigued you with the question! And if you have answers you’d like to offer, I promise due credit if I wind up using yours alongside mine in the paper…


1. On the circumstances leading to this reform see most easily Alex Nobes, “The economic and monetary policy of the Byzantine Empire under Alexios I Komnenos” in Rosetta Vol. 11 (Birmingham 2012), pp. 56-71, online here, but you might wish to compare Michael Hendy, Studies in the Byzantine Monetary Economy c. 300-1450 (Cambridge 1985), pp. 513-517 and Alan Harvey, “Financial crisis and the rural economy” in Margaret Mullett & Dion C. Smythe (edd.), Alexios I Komnenos. Papers on the Second Belfast Byzantine International Colloquium, 14-16 April 1989, Belfast Byzantine Texts and Translations 4.1 (Belfast 1996), pp. 167-184.

2. For the actual coins, the best guide is indubitably Philip Grierson, Byzantine Coins (London 1982), pp. 211-228, esp. pp. 223-228.

3. Simon Bendall & David Sellwood, “The method of striking scyphate coins using two obverse dies, in the light of an early thirteenth century hoard” in Numismatic Chronicle 7th Series Vol. 18 (London 1978), pp. 93-104.

4. David Sellwood, “The Production of Flans for Byzantine Trachy Issues” in D. M. Metcalf & Andrew Oddy (edd.), Metallurgy in Numismatics, Royal Numismatic Society Special Publication 13 (London 1980), pp. 174-175.

5. Strength: as well as the article linked, Cécile Morrisson, “La concavité des monnaies byzantines” in Bulletin de le Société française de numismatique Vol. 30 no. 6 (Paris 1975), pp. 786-788, criticising the work of Hendy cited below, for which reason no doubt Hendy not unjustly responded in Studies in the Byzantine Monetary Economy, p. 510 n. 313, “Neither explanation [that of Grierson mentioned below or Morrisson’s] is totally satisfactory by itself, as neither takes full account of the curious inconsistency of its early usage”, and indeed I could show you flat nomismata contemporaneous with the earliest concave ones right here where I write. Indicator of metal quality: Michael F. Hendy, Coinage and Money in the Byzantine Empire 1081-1261, Dumbarton Oaks Studies XII (Washington DC 1969), p. 6; Alfred R. Bellinger & Philip Grierson (edd.), Catalogue of the Byzantine Coins in the Dumbarton Oaks Collection and in the Whittemore Collection. Volume Three: Leo III to Nicephorus III 717–1081, by Philip Grierson, Part I: Leo III to Michael III (717–867) (Washington DC 1973), pp. 5-7, to which cf. Morrisson, “Concavité des monnaies byzantines”, p. 787, accepted by Grierson, Byzantine Coins, pp. 197-198. I don’t yet have cites for the stacking or tiddly-winks theories, alas; they are much repeated but never with attribution. For the idea that the flans were now too big and had to be reined in, see Franz Füeg, Corpus of the Nomismata from Basil II to Eudocia 976-1067: corpus from Anastasius II to John I 713-976 with addenda; structure of the issues 976-1067; the concave/convex histamena; contribution to the iconographic and monetary history, ed. Italo Vecchia, transl. H. Thomas Hofmänner (Lancaster PA 2014), pp. 103-124 esp. pp. 122-124.

6. This last point, though obvious, I had to have pointed out to me by Dr Rebecca Darley.