If you look closely at my OP, you will see it says these coins will be stamped, , there will be no mint. These will be rough looking coins I would assume, and are going to be made like ancient greek coins where. Each one will be a little different
I wonder if any other coin makers have stamped their coins vs using a mint. There's a risk these coins will be very handmade looking and a lot of unhappy customers expecting something else. Perhaps you should show a finished product before asking for payment, even if using escrow.
Why not use a mint and charge more to recover your costs?