As Diver Down mentioned, I've seen real ones thinner than yours. Start with a magnet, then proceed to an acid test. Weight and diameter probably won't mean a whole lot on very worn or shipwreck coins.
Took the two 8 reales, to pawn shop, and they said beyond doubt, they are silver, so looks like coins are legit, good adder for my modest collection......
Should I get them graded as authentic![]()