The "D" Denver mint coin looks decent. Maybe from a mint set. The "S" coin is interesting. The San Fransisco mint produced three variations of that coin. Two proofs and an uncirculated coin. All were issued in sets. There is a clad proof, made from copper and nickel, and it weighs 5.67 grams. The other proof is 40% silver, often called "silver clad". It weighs 5.75 grams. The uncirculated silver clad coin weighs the same as the proof silver clad. The photos show the coins having a similar finish. If they are an accurate depiction of the coins in hand, I would say the someone broke the silver clad, uncirculated set apart and the quarter ended up in your hands. Nice find!
It's not just called silver clad, it IS silver clad. The outer layers are 80% silver and 20% copper. The core is 20.9% silver and 79.1% copper. It nets out to 40%. The core is a lighter silver color (vs the copper core of the copper-nickel clad coins) so it's not always as visible at first glance.
