I bought a new ring and noticed that it isnt stamped. what does it mean? what is the ring made of?

the ring was $20 and said sterling silver on a sign above the table but all silver jewelry I have is stamped 925 and this ring isnt marked at all. what is it really made of? and will it rust or tarnish?

925 is the marking for sterling silver but there are other qualities.

There's a big demand for precious metals right now. Take it to a good pawn shop and ask what they're willing to pay for it (not pawn it). If it's valuable, they'll want to buy it. If not you know the answer.