Watch List notes:

UNCERTAIN WESTERN EUROPE. Æ. Countermark applied mid 1st century AD(?). M shaped countermark applied twice (or MM?) on a sestertius of Caligula (RIC I 37). Apparently unpublished in the standard references. Host Fine, c'm VF, brown river patina, some roughness.

From the Richard Baker Collection. Ex Classical Numismatic Group 55 (13 September 2000), lot 1137.