Actually it has a very tiny stamp inside which looks like 925, but it was sold to me as S80 so that is how I listed it. I think S80 is silver plating. Thanks for looking!
S80 =This means that the item is 80% silver and 20% alloy. Sterling silver is 92.5% Silver and 7.5% alloy. Many silver items produced in Mexico are marked 800 or 80.0.