IMO.. There should be a desired effect and then a choreographed sequence of motions that achieve the desired effect and in doing so we should try to eliminate suspision while attempting to astonish and creates a feeling and sense of magic being performed (even if it is just a vanish). So I am not sure but to me vanishing, dematerilizing or turning invisible are kind of the same. But if you can translate this to spectators then it can I guess work for you. If they never see the coin does it vanish? I have to say the Egg ???

The coin they are watching - that they believe you are holding in your hand, please.

Jon, it's a strange thing--you know that coin that you gave me when I asked to borrow a coin--it looks exactly like a coin I had about six months ago. Now you're going to say that I'm crazy, recognizing a coin as if it were my baby, but this particular coin I can't forget--here's why: