The ones you chose from
parthia.com are earlier than yours. The
parthia.com coins
still have a very recognizable
bust on the
reverse. With time this must slowly becomes a
collection of lines. Yours is more toward the later
types than the ones you have chosen.
As for being
billon, it is most like that, but the silver content is so low, it might as will pure copper or bronze.
Forgot to mention that
Sear lists it as Kamnaskire VI(?). These later rulers of the Kamnaskire's line are very difficult to tell apart, and no one really knows how many there really were.
As for the
price you paid, that is a
very good price for a
tetradrachm. But again, with the bad
reverse, you will have a tough time if you ever decide to resell it.
