I made this to display pressed coins that I got from my recent trip to NYC. There are two sizes, one tall and one short. They attach together with a small pin at the back to make larger displays. You can combine any combination of small and large as the pinhole is at the same height on both. 

I printed at 0.3mm with no supports and found the pin was a touch too large and needing cutting down slightly. Better calibrated printers might have more success.