The only one of these that is possibly a
Christian symbol is coin 4.
1) The symbol on Mar's helmet is a
star, typically 8-pointed, sometimes 6-pointed
2) This
type dates to 307-308, before Constantine's supposed conversion. I've never seen one with a star-type design (normal depiction seems to be of inside of
shield, not outside where the design would be), but at this date it would be a solar symbol if it exists.
3) The symbol is an 8-pointed
star (
RIC VI Rome 377)
4) This is
RIC VII Aquileia 124, dating to 334-335. The symbol may be a crucifix-type
cross, although it often has the form of a "T" with a dot/ball on top. It'd not be surprising to see a
Christian mintmark at this date (at the same date
Arles was using an unmistakable
Chi-Rho), but I'm not sure this one is a slam dunk.
Ben