It's an intriguing mystery, but I don't know if there's enough there to work with. What you take to be lettering could be, or could just as likely be denticles instead. I'm stumped. It's certainly very old, though, and I think you are right about it being ancient.
Durotriges staters (billon or AR) of Celtic Britain have clustered dots and would be the right size. Where was this coin found?
I received it from my father a couple of years ago so I don't know where it was found ... thanks for all the help btw guys!
I've got some with totally obliterated obverses like this one - quite a few that came in several hoards of uncleaned coins that I bought. If one can ID the reverse then it is still possible to make an attribution. It doesn't look like a familiar type to me, though, so I'm stumped as well. I would guess that it might be a greek or a greek imperial...
