Mining TNet's archives, I found this unanswered posting. While the OP's coin lacks certain elements, it still may be real.
(How's that for an evasive answer.) If the coin were complete, it would look like and be attributed like this:
Pansa was a Republican moneyer and Consul in 43 BC; probably the adoptive son of the C. Vibius Pansa (q.v.) who issued coins in first C BC.
Don in SoCal