Marks on Ancient Coinage

Many ancient coins have man-made marks that were added to the coin after the coins left the mint. These marks fall into three broad categories.

Test Cut

Test cuts were made with a knife or chisel in order to expose the interior of a coin to test whether the coin was real (that the metal was good) or if the coin was a forgery¹, as often forgeries were base metal that was plated with gold or silver² where the plating was not thick enough to withstand a deep cut. Although test cuts can be found on coinage of any era as anyone with a tool can make a cut, until the advent of the specific gravity test in 250BC, no less-intrusive method than cutting into the coin provided a truly reliable test.² Although some coins exist with multiple cuts, typically one cut was sufficient to convince the tester that the coin was genuine.¹

Banker's Mark

Banker's marks are similar to test cuts in that they were used to affirm a coin's validity, but marks were often letters or shapes, rather than simply punches. The letter or symbol identified the private merchant or government official (such as a civic banker who was stationed at a port who validated currency that was to pass into the country) that was satisfied that the coin was genuine.³ Banker's marks can be found frequently enough placed such that the ruler's portrait is not impaired by the mark - this appears to have been a conscious choice, rather than by accident.¹

Countermark (Counterstamp)

Countermarks (counterstamps) were used for a variety of purposes. As given by Baker⁴, reasons included:

To extend the geographical range that a coin would be accepted as legal tender.
Coins issued in a Roman mint for circulation in provinces, or coins struck in a provincial mint for circulation in other parts of the empire, could be stamped to ensure they could circulate elsewhere. Similarly, locally-struck provincial imitations of Roman coinage could be marked to indicate they had Imperial approval.
To continue in use a coin which had been in circulation for a considerable period of time.
Worn coins could be stamped to change or reaffirm their value, or to give coins of a previous ruler a guarantee of acceptance by the current ruler.
To designate a new authority usurping the coins of another for their own use.
Coins could be marked by the followers of a revolting general or legion, sometimes to deface the portrait of he who was being rebelled against. Also, local coinage could be stamped with Roman or legionary countermarks so they could be used as legal tender by the legion, such as Legion X, Fretensis stamping X, XF or LXF on coins of Judaea and Samaria.