RIC 930
Most people are familiar with the Roman as of Antoninus Pius with the reverse legend BRITANNIA COS IIII SC (RIC 934). However, fewer will be aware that there is a corresponding dupondius (RIC 930). From a brief survey of examples in trade of these two coins it would appear that the as outnumbers the dupondius by at least 3:1.
RIC 934
It has long been suggested that the Pius Britannia coins may have been struck at a mint located in Britain, albeit from dies supplied by the mint of Rome. One of the earliest records of this suggestion is in a paper by F A Walters in A Find of Early Roman Bronze Coins in England (NC 4th series, volume 7, 1907). He noted that the Britannia coins in the hoard were of poorer fabric than other contemporaneous aes, although the die cutting was good and so postulated a temporary mint establishment.
Malcolm Todd, whom I met, incidentally, on a number of occasions when he was asked to review my research at Durham in the 1990s, noted in Romano-British Mintages of Antoninus Pius (NC 6th series, volume 6, 1966) pointed out that this may be supported by the almost exclusive British findspots of the type.
However, when you consider other types of aes in the period 81-192 AD there is a systematic approach to coin distribution, not just to Britain but across the empire (Hobley, BAR Int. Ser. 688, 1998). The Britannia dupondii and asses were, apparently, sent to Britain because of their reverse type and the relevance to the province.
Furthermore, the late John Casey told me of some unpublished analyses that he had commissioned of the Britannia coins and was able to demonstrate that the alloy used was consistent with other aes of Pius. If metal and dies were centrally produced there is no reason to transport specie and dies to then strike coin in the province, there is no advantage to that when finished product can be just as easily sent.
