I was going through a few coins I bought in an uncleaned lot and came across this one. I'm not looking for an ID, just an explanation of the tab looking thing sticking out. On a higher end coin I'd assume it was a fake but I doubt somebody is making fakes of this type and seeding uncleaned lots with them.

My first thought is that it could be the sprue left over from when the flan was cast. I'd be a little surprised if it survived the coining process and still looked like that though, and it's something I haven't seen before. Is there an alternate explanation?