A lot of countries use related curves of constant width for their coins. It makes it easy to tell, say, a Loonie from a Toonie by feel, yet they can still be au

A lot of countries use related curves of constant width for their coins. It makes it easy to tell, say, a Loonie from a Toonie by feel, yet they can still be automatically sorted by sliding them through a slot without them needing to be oriented in a particular way. I've never seen a triangular coin like that though. That would be pretty cool.