I told my mate that the new £1 coin was going to have 12 sides

A dodecagon

On a related point, it blew my mind the first time I saw a Toonie. I was like, what's this? A two tone coin? It's like a little coin getting a hug from a big coin.

A coin has three sides the two main faces and the ridged Side stretching around the entire coin

There's the edge