Definitely looks like half of a one real Spanish silver coin. Lots of silver coins were cut for change in the past but I'm curious how that one ended up that way. Looks more broken than cut. Congrats on a sweet find!
trace out the diameter with a compass, appears it will fit nicely for a 2 Real, then search 2 Real for portrait match and now you have the date range for that king. looks like they tried to cut it, gave up & broke it---still too cool!
It's a Spanish silver... dang man. It's broken as opposed to cut. There appears to be "score" lines across the face, where someone tried to cut it, but it must have broken instead, oops. looks like a 2 real... almost quarter size.
South Louisiana is a good place to find those. btw it's certainly not a 2 reales. Way too small for that. It's a broken half real, or as they called them back then in Louisiana, it's "a picayune."