1960 Half Penny - Strange Edge Flake - Any Ideas?

Hi all,

I was just rummaging through a bag of old pennies and came across this strange fault.

I've never seen anything like this before and I can't figure out how this damage was caused. It looks as if the little tag or flap is part of the original coin surface, not something that got squashed onto the coin as it blends perfectly into the rest of the surface.

I've tried to get some close ups but the lighting makes it tricky to see exactly where and how the tag is attached and folds over the edge. I'll get some better ones uploaded soon.

If anyone has any ideas as to what has happened, I'd love to hear them, cause I haven't really got any.