I didn't find a satisfying design here, so I created my own one.
The sample is printed with ABS, bed temperature was set to 100°C, nozzle temperature to 235°C.
Used some sand paper for cleaning and finally smothened it with acetone.
UPDATE FROM 08-17-2021:
I ported my old model from TinkerCad to FreeCad and changed it a bit to make it printable without support. The FreeCad source is included, so you may adapt it for other coin sizes. I also changed material from ABS to ASA-X.
CoinHolder.FCStd | 66.9KB | |
CoinHolder.stl | 41.5KB |