if you coin meisters use foreign or obsolete coins, don't you get problems with specs assuming they're fake or gimmicked?
I used to think the same thing, however the only real advantage I can see to using a standard uk coin is that you can actually borrow the coin off a spectator.
If asked why I'm using half dollars or old pennies, or even mexican coins! I just say because they are bigger and so more visible, but believe it or not no one really cares. All they see is a coin vanishing or appearing or whatever it's meant to be doing. In short all they see is the magic.
It's a bit like using bicycle poker sized cards in the UK. Didn't you think that when you first started using them that people would ask why you are using these funny looking extra large cards? I know I did. After all, most lay people in the UK are used to bridge sized waddington type cards.
I know its not exactly the same thing but it is the same principle.