I wish you every success.
As a boy I visited the Cadbury's Chocolate factory near Hobart.
The choccies used to travel past an examiner on a continuous belt of some transparent material (maybe PVC or vinyl).
Below that was a mirror, so both sides could be examied, almost at the same time, and with onlyone pass.
Your idea uses cameras, I take it, to enlarge as well as record the image.
How will they pass: in a horizontal plane; vertical; something else ?
You're dealing with circulation coins, so no need to get hung up on handling issues ...
Peter in Darwin