It might be time to start digging through your piggy bank. Coin error expert Mike Byers has discovered a 1970-S Washington quarter that was struck over in 1941 Canadian quarter, and you can see the faint trace of the other coin. The strange coin was discovered in a bank safety deposit box somewhere in California and was recently sold on eBay for an asking price of $35,000! It turns out this Frankenstein quarter is part of a collection of minting errors that were released by the Secret Service to the state of California, and then auctioned off to an unknown recipient. Before you get too excited, bear in mind that this is a proof coin that was not intended for general circulation. It would be unusual to find it out in the world. Numismatic Guaranty Corporation [NGC], a third-party client certification company, has confirmed it is legitimate but could not provide a reason it was created. Was it a freak accident? Perhaps some eccentric employee at the San Francisco mint decided to make things interesting? Take a look at the image below to get an idea of how to recognize this rarest of error coins.