On another board, the question was asked whether commemoratives were ever silvered. Below is an example from Alexandria with a good bit of the silvering intact. You do not find examples with silvering very often though.
A.D. 333-335
19x17mm 2.7g
Obv. CONSTAN-TINOPOLIS laureate, helmeted, wearing imperial mantle, holding scepter.
Rev. Victory stg. on prow, holding long scepter in r. hand, and resting l. hand on shield.
SMALB in exergue
RIC VII Alexandria 64