Friday, 8 May 2015

The Iceni hypothesis — part sixteen

Cassiterite from Cornwall
photo: Rob Lavinsky, – CC-BY-SA-3.0
This hypothesis grew out of several observations: noticing die links on two closely located coins where alleged silver pellets were also found reminded me of another "scattered hoard" where such pellets had been found and I had wondered, at that time, if a council site, rather than a hoard had been discovered. I had an opportunity to test my idea by describing the features of a site for Dean Crawford based only on a description of what he found there. My hypothetical description was accurate on all counts. It was the analysis of that pellet, though, that had me really questioning the nature of the site and its implications for Celtic coin studies. These ideas have been developing for a few years now.

Two types of sources for the metal in British Celtic coin alloys has been identified: through the recycling of earlier coins and from mined metal. The former was determined by gold issues keeping close to the Gallo-Belgic three part alloy for gold coins; by the presence of tin in other coins which was associated with their copper content and was identified as being present in scrap bronze used in the alloy instead of copper directly from ore; and by various other trace elements. While I still think that much of this is still true, the strange usage of tin for different purposes at the Dobunni site in the pellet and the ingot. also makes me think that some coins currently believed to have been made from recycled metal are actually made from mined metals, at least for the Sn content.

Finding tin in Celtic gold coins in any significant (alloying) quantities is rather unusual but it does exist in British D; Lb (late); Lc; Ma; Mb; Qa (late); a Commios stater; and a British Na stater (numbers from Cowell's analysis of 1992, and I have taken the lower limit to be 2% Sn as that is the lowest recorded Sn content in Greek bronze coin alloys (Massalia).) Of the locations of all of these types, the Dobunni are not distant neighbours save for the British Na (Iceni). From the west end of the Jurassic Way to Norfolk is a trail of breadcrumbs in the forms of a small ingot of white gold of an alloy in keeping with some Norfolk wolf staters but containing tin in association with a pellet and a Thurrock potin containing high levels of tin; a trail of Thurrock potin stray finds both sides of the Jurassic Way and pointing in the same direction (to Norfolk); famous and high status metal work (frequently associated with Dobunni) all along both sides of the Jurassic way, in Iceni territory at its closest point, and at its end far above the coin-using tribes in the north; an Antethirig at both ends of the Dobunni-Iceni funnel which seem to be at about the same time; and the knowledge (but no figures, yet) of tin in late Snettisham base silver-gold torcs.

Why would tin be deliberately added to any metal alloy? Hardening is the immediate answer that comes to mind but tin, at other times, has also been used as a debasing metal for silver as it does not radically change its appearance like copper can. A lot of the seigniorage seen in lowering coin metal purity was based on the cost of metals distant from their source or transportation, as well as subsequent coining expenses, and I think it is thus valid to see something similar in the quality of ingots or casting pellets and the profit from tin would have been fairly great for the Dobunni who were both adjacent to the tin source and had fairly friendly relationships with other tribes. The Dumnonii appear to have provided the Dobunni with tin debased with copper (if that turns out to be the source of the pellet), but at a lower percentage of copper than the Dobunni were passing on to their customers. This is a pattern you would expect to see in trade. Ptolemy I of Egypt hid an awful lot of seigniorage from traders by insisting that their money had to be changed to Egyptian money, which happened not to be of the Attic standard they were used to, but an entirely new standard of his own invention. Then he changed the ratio of gold to silver values. Ptolemy was a Greek, the traders were Greek. The only way that Ptolemy's deception could have been detected (or even designed not to be detected) would have been by algebra, but the Greeks did not know algebra. The native Egyptians did, though. I suspect one of them in Ptolemy's time did quite well for himself. Egypt minted a lot of big gold coins over the subsequent years.

Monday: will all of the pre-Roman British dynasties join Geoffrey of Monmouth on the spoil heap of British history? Have a great weekend.

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