I can't even tell if it's a modern "shipwreck" coin or an ancient. I suspect the former, if the white stuff at 10 o'clock in the top pic is a piece of coral. There's not a single feature I can point to that couldn't be explained by corrosion.
It presumably had enough sentimental value to a previous owner (perhaps the finder) to have it embezelled. But detached from its context, I'm afraid its identity might have to remain a mystery.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis