Coin spinner

This is a slightly modified version of the [Money Spinner](https://www.thingiverse.com/thing:1937473) by GeoffB. I had a lot of 20 euro cent coins lying around, and wanted to use those. This is a good way to put some copper coins you have lying around since your last trip to use.

Instead of selecting from a short list of coins, now you have to put in the size of your favourite coin directly. Look it up at Wikipedia, do a web search, or use a calliper. The pre-set size is for 20 euro cent coin