(sorry about that sentence, it reads rather strangely)
So, the Mesopotamians used the silver shekel, and (I believe) silver mina, with their value based on the amount of grain. Using a base sixty (?) system, I'm pretty sure I read that 1 shekel equalled about sixty mina, and each mina had a 'base price' of about 10 grains I think?
So yeah, not 100% sure, but my players won't know any better, so everything's cool.
I'll post about the Mesopotamian pantheon soon, as I've got it all sorted out (i.e. who was descended from who, their domains, for lack of a better word, and which cities that they're patrons of).
I'm also finishing off a not-quite-accurate-but-good-enough-for-me hexmap of Mesopotamia.