Nicely performed.
It's very rare indeed that I use a bite out coin but they can be good fun and I only do so when around a charity box.
Palm one coin, say a 10p and then bite out and restore and then switch coins before dropping the real one into the charity box. You tend not to get hassled by people wanting to see the coin. Collection buckets are also great as you can appear to dip in and then throw the coin back into the bucket afterwards.
The specs always start looking for the coin in the bucket whilst you walk away.
You've got Children in Need coming up soon so there's a good opportunity to try it out and make it look totally impromptu.
Member of the Magic Circle & The 2009 British Isles Close-Up Magician of the Year
It's not really an optical illusion - it just looks like one!