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3. The Minting Process
In the early Republic coins were cast in moulds. The majority of coin types however were made from blanks called flans (or planchets) which were then struck between engraved dies.
Flans were pieces of metal that were the correct shape, size and weight for striking into a coin. They were made in several ways – being cast individually or in strips joined by narrow pieces of metal (Plate 1). From the 3rd Century they appear to have been cut with a chisel from a bar or punched with a circular punch from a sheet of metal. Old coins could also act as flans and be overstruck to form new coins.
Plate 1: Part of a mould used for the production of flans.
The obverse or anvil die was held in position on an anvil. A heated flan was then held in position over the anvil die by one member of the team (the suppostor) with a pair of tongs and the malleator then struck the reverse or punch die with the hammer to stamp the coin. The reverse of a denarius of T. Carisius dated 45 BC is purported to show an anvil, hammer, tongs and wreathed reverse die, representing the tools of the mint. (Fig. 1) It could well be, however, that the reverse image is in fact the laureate pileus of Vulcan which together with the hammer, anvil and tongs appear in both Roman and Greek art representing the "smith of the gods".
Fig.1: Drawing of the reverse face of a denarius
of T. Carisius, dated 45 BC, showing either
minting tools or the accoutrements of Vulcan.
Several estimates have been made about the life of the dies and the output of the teams of suppostores and malleatores. A die could shatter on its first ‘strike’. If it survived its early strikes and hardened as a result, its life depended largely on the nature of the flans. With flans of hard metals, obverse dies would probably produce about 10,000 coins, whereas with gold the figure could rise to more than 30,000. (Reverse dies came in for heavier treatment so would presumably have a shorter life than obverse dies). A good team of coin stampers have been estimated to produce around 1,000 coins per day. The patterns of die use adopted depend on the mint in question. The simplest system would have been to use hinged dies where the obverse and reverse dies were paired for life. A painting of cupids in the House of the Vetti in Pompeii appears to suggest that hinged dies are being used in the minting process. It is difficult to know whether or not hinged dies were used at Ostia but it may not have been the method employed as only "die duplicates" would have been produced and the evidence doesn't entirely support this.
Where dies were used separately, the teams would replace 'failed' dies whilst keeping the serviceable die in use. This would give rise to die use patterns such as:
Obverse 1 / Reverse 1... Obverse1 / Reverse 2...Obverse 2 / Reverse 2.....Obverse 2 / Reverse 3
and at the same time "die linkage" would occur for which there is more evidence at Ostia. Whether or not there was any pattern in die use depends on how many dies an officina had in use at any particular time. If they possessed more than one and these were handed out randomly at the start of the shift by the administrator, die use patterns would be very difficult to track. If each team were given the same pair of dies at the start of each shift, then patterns may show up. Large numbers of coins need to be studied for real evidence of these phenomena to appear.
Dies were made of either bronze or iron. Few remain, as they were probably melted down at the end of their usefulness for security reasons. Any that do survive were probably stolen from the mints or are likely to be counterfeits. All dies were individually hand cut by the escalator using a burin, punch and a drill. Diamond may also have been used as it was known to have been used by the gem engravers of the day as described in Book XXXVII of Pliny's "Natural History". On a number of Imperial coins from the 3rd and 4th Centuries AD, die "centration dimples" have been found. On one example of RIC 35 minted at Ostia, such a dimple can be clearly seen in the centre of the coin. On the die, this would have taken the form of a small depression. So, what is it's function? My suggestion is that the depression is for one of the points of a pair of compasses that were used to 'score' the part of the die where the beading was to be engraved. So, why does the dimple appear on some coins and not on others? After the beads had been engraved, the central area of the coin would be 'filled in' with the rest of the image. In RIC 35, this area contains the raised legs and hooves of the two horses which were engraved over the dimple. On the coin below, that central area is not engraved so the dimple can still be seen (Plate 2).
Plate 2: Centration dimple.
There is no convincing evidence that a process called hubbing took place, where a cutter would make a preliminary impression of a coin type, leaving perhaps only the officina mark to be added prior to use. One possible hub exists in Madrid but no coins stamped from this die have been found, so once again, counterfeiting is suspected. What is known is that some mints had die cutters for each individual officina, whereas others had a pool of cutters making dies for the whole mint.
The dies for both faces of the coin result in a wide range of variation in the finished product, showing the individuality of the cutters (Fig. 2). Individual coins show variations on both faces due to the operating system used in the mint. The type of coin produced would depend on the types of dies issued at the start of the shift. If dies had been kept separate outside working hours, a great deal of variation could result – security would hardly allow pairs of dies to be kept together overnight.
Fig. 2: Diagram of the obverse face of a
Maxentian coin showing differences in
the alignment of the laurel wreath and
variations in the detail of the beard.