Now I'm home with my books, I can confirm: it's a Roman as. At 28mm, it would date from sometime around 100 BC, plus or minus a couple of decades. The abbreviated consul's name should appear on the reverse (ship) side, but the only text I can read is "ROMA", in the exergue.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis