This is a rather beat-up example of a Spanish "Reyes Catolicos" silver real. We've seen quite a number of "tourist fakes" of these coins, but this one seems genuine to my untrained eye. I believe the same design was used for several denominations, so we'll need to know the size to narrow down the ID further.
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