A very small group of Proof errors recently came from a collection that was auctioned by the State of California. The U.S. Secret Service inspected and released this collection to the State of California determining that it was legal to own. The State of California then auctioned the collection and it has been dispersed since the sale. This 1970-S Proof Washington Quarter struck over a 1941 Canadian Quarter was part of that collection and was certified by NGC. There are only a few known U.S. coins struck over Canadian coins. This is a dramatic mint error since it involves two different countries and 29 years between strikes.