Thanks JazzO for straightening out the info re coins.
On subject of coin sizes :
A friend who is a neurologist uses a standard old test for patients .. you are asked to close your eyes and identify the coin he places on your fingertips ... the coin size helps a bit but people's guesses soon deteriorate .
He told me that he was amazed just once : when an older gentleman patient named every coin correctly through a triple length test. Turned out the gentleman was a retired fare collector on a bus line. Being able to identify coins by touch was a necessary part of the job. He could spot a "slug" by touch alone!
Now there's a party trick if I ever heard one!
wow