If it were me, I'd just spell "coin."
Sure, the "F" handshape can be used to show small round objects (like a small pole, buttons, or COINS).
The "F" handshape can even show movements of your eyeballs. Yes indeed, that "classifier F" handshape is flexible and can show pretty much any small round hole.
Ahem, and therein lies the problem. The "F" handshape could be held up and the "circle" could be used to represent a single coin -- but it could also be used to refer to someone's [cough] ...er...rectum hole. So, you've been warned. Make sure you establish plenty of context before you go waiving around your um, hole. (So as to not be misunderstood.)
CL:F
Also see: COINS
Notes: