Examining Roman republican coinage, besides the frequent bankers marks applied during the coins life in circulation, other marks and gouges can be observed. The initial reaction is to dismiss the apparent damage as being from careless use, or strikes while in the ground from spade or plough, but this is not often the case.
In 1993 Clive Stannard published a paper that linked these marks to being done in the mint. The scooped gouges showed signs of catch marks where the tool responsible had juddered in its application. By studying the Cosa hoard and the holdings of various institutions, including the British Museum, the Ashmolean Museum, the ANS collection and significant private holdings, he concluded that, because of the uniformity of the mark and the judder lines, the marks were deliberately made to adjust, in fact reduce, the weight of the coinage.
He then had to consider whether they were made al peso (reduce the individual weight of a specimen) or al marco (to increase the total number of coins made from a defined weight of metal). Through the use of statistical analyses he concluded that the marks were applied to heavier specimens in a batch of production, candidate coins likely picked by hand, to provide silver to remelt to correct the required number of coins produced for a given weight of metal.
This these gouges are referred to Stannard al marco marks.
Stannard, C. "The adjustment al marco of the weight of Roman republican denarii blanks by gouging" in Metallurgy in Numismatics 3 (London, 1993), pp 45-70
