it is 12mm and 1.5g It used to look something like this, though the workshop is Z on the modified coin This coin was issued around A.D. 328 and was modified at least fifty years later into a weight. The tremissis was a small Byzantine gold coin introduced by Justinian I in the 380's, with an average weight around 1.5g. Clipping gold coins was a problem, so people made these weights to check the gold coins. Here is an excerpt from the Codex Theodosianus from the time of Julian II talking about the problem of clipping or "nibbling away" 'Emperor Julian Augustus to Mamertinus, Praetorian Prefect. The purchase and sale of solidi are impeded if the solidi are clipped or diminished in size, or nibbled away, to use the proper term for such avarice, since some persons refuse to accept such solidi on the ground that they are light and inadequate. Therefore, it is Our pleasure to establish in each municipality an official called by the Greek word zygostates (lit. weigher), who by reason of his trustworthiness and vigilance will neither deceive nor be deceived, so that in accordance with his judgment and reliabilty he may settle any dispute that may arise between the seller and the buyer with respect to solidi. - Given on the ninth day before the kalends of May at Salona in the year of the fourth consulship of Julian Augustus and the consulship of Sallustius [= April 23, 363].' (Cod. Theod. XII.7,2).