There's this gold coin on ebay, 1903 McKinley Gold Dollar and the seller has it listed as an error, I don't think so, but what you all think? And check out that sale price! https://www.ebay.com/itm/800322323408
It was mounted to a pin or something similar. It seems kinda silly to me to think that the mint could have produced that. There would have to be a big hole in the die but then where did the metal come from to fill it?