Welcome
You guessed it. This happens so much on beaches, that there must be lots of sick people out there chucking them into the sand in hope that people will dig them.
PS. Having said that, if it gave you satifaction, maybe they are angels.
Yes, the corrosion gives it away as a fake. But I'd be happy to find it nonetheless. Sure beats the pull tabs and bottle caps I always come up with at the beach.