I was looking for W's and i came upon these. I forgot all about the s mint mark did I read correctly that proofs are only silver?

S mintmark for 2017 Indiana quarters were struck for circulation, clad proofs and silver proofs 2017 S San Francisco 919,060 2017 S Proof San Francisco 689,235 2017 S Silver Proof San Francisco 496,626 and for Georgia 2018 S San Francisco 816,660 2018 S Proof San Francisco 658,438 2018 S Silver Proof San Francisco 350,820