Might be a replica of a Spanish coin. You can buy them on eBay by the bucket for about 15 bucks. This was one of my first ever finds (3 inches under in backyard) and raved about it until discovering it was fake about a month later. Nevertheless exciting...happy hunting.
It's still a good find, just not great, and it's fun digging them, better if it was real, I dug 4 on a beach in one day, almost broke my machine after the fourth haha