Being found in Florida I would suspect it could possibly be a Spanish copper, but I can't see any identifiable detail in the pics. The "E K" counterstamp is really neat though and looks like a pretty old stamping.
The E K is pretty much the only letters that are visible. I suspect it was down there a long time. On the other side with a magnifying glass it almost looks like a head it weighs more than a quarter but less than a half. Rang up high as heck on my Garrett. Thought for sure I had a 90 percenter. I’ll try to clean it more later on and post better pics.