Check your pockets and hit up a coin dealer! Your U.S. quarter worth could actually be in the thousands. If you have a 1970-minted quarter, keep it in a safe place and get it looked at. It was recently discovered that people are paying up to $35 thousand on eBay for the rare coin. Who knows if the mint error coins are worth that much really but hey, who are we to judge?
Why is the 1970 S proof Washington quarter so valuable? It's actually a mint error that is driving the price so high. This version of the 1970 quarter was actually formed over top of a 1941 Canadian quarter. If you look on the back of this coin, you'll spot an upside down 1941 mark on the back. It's located above the word "dollar." It's honestly a significant amount of detail the average person would probably miss. Who would notice the slight design of the Canadian quarter?
The man selling the coin for $35k on an eBay listing is Mike Byers, and he's a Numismatic (i.e. big in the study of coins) and has actually written a whole book on minting proof errors. Would anyone actually pay this amount? People love collecting rare coins but paying the equivalent of someone's yearly salary seems like a lot.
Don't get too excited, though! The Canadian coin (partial Canada quarter?) wasn't actually circulated. It's known as a proof coin which means it was basically a rough draft of a coin, hence all of the proof mint errors. In fact, after the minting, the collection of mistake quarters was given to the state of California where it was then auctioned off. Where 1970 S Proof Quarters are now is anyone's guess, but there's no harm in checking out your loose change and couch cushions! You could have a gold mine hiding in there!