Watch List notes:

M Iunius Silanus, Rome Mint, 145 BC.
Helmeted head of Roma right, behind ass's head, X below chin;
The Dioscuri with spears riding on horseback to right, beneath M_IVNI, in exergue ROMA.
Crawford 220/1. Nice patina, few scratches. Fine. Size: D: 18.2mm; 3.47g