Coin Holder For Pictures?

Think differently. Lay the coin flat, and bring the camera to it. Keeping the coin and the lens plane of the camera parallel is extremely important to good coin photography, and that's a heck of a lot easier (and safer for the coin) if you mount the camera on a tripod looking down than trying to balance a coin on its' rim.

That's because the coin and the lens aren't parallel; the depth of field involved in macro photography vs very narrow. There's nothing stopping you from using a tripod in place of a copystand - good copystands capable of holding a larger camera are not cheap, and if you already own a tripod it'll save you the price of another coin.

Here's the setup I used before I bought my copystand. It worked perfectly: