An attached, fold over lamination.
I don't think so. If it was a lamination folded pre-strike it would be flush with the surface and it isn't. If it was lamination folded post strike there should be a rough depression area where the folded lamination material came from and I'm not seeing that either. It originally had a matching piece above the date and it's removal has not left a depression or rough area either. A retained strike though? Maybe but once again that should be flush with the surface. I suspect something stuck to the coin.
But even if it is an error all the needle scratches from trying to remove it would have removed most of the value.