The question I asked yesterday about that intaglio were answered in the forum by JMM and offlist by WA ... just so we have it available here though (and to answer the queries of those wondering too), it transliterates as:

IAW SABAWQ ADWNAIE

... the 'Q' is a theta for those of you who aren't familiar with beta code; in 'English' it would be Iao Sabaoth Adonai(e)Whatever the case, it does point to the owner either being Jewish or (more likely, given the accompanying image of Janus) a proponent of Gnostic mysticism/magic. So -- as JMM pointed out -- it ain't 3rd/2nd century B.C.. More likely late(r) Roman.