COIN (ROMAN)
Silver Republican legionary denarius of Mark Antony, c.32-31 BC, travelling mint, RRC 544/26

Stamped with an 'N' on the obverse which is a banker's mark.  Were it an imperial or official countermark it would be a punched die (Sam Moorhead pers comm).

This coin likely came in with the Roman army during the 1st century AD.  However, Mark Antony denarii are known to have remained in circulation until the 3rd century AD.
Ruler: Republic
Denomination: Denarius serratus (Roman Republic)
Material: Silver
Mint: Moving with Republican issuer
Obverse: Praetorian galley right with rowers, a standard is placed at the prow
Obverse legend: ANT. AVG/IIIVIR. R. P. C.
Reverse: Three standards, a legionary aquila between two signa 
Reverse legend: LEG XII
Dated: -32.0 to -31.0
Weight (g): 3.06
Diameter (mm): 18.4
Thickness (mm): 2.1
Completeness: Complete
Parish: Lanivet
District: Cornwall
County: Cornwall
Region: South West
Discovery method: Metal detector