1970, proof quarter worth a bundle

[Gold Maven]

I never heard of this, but a "few dozen" 1970-s proof quarters were struck over canadian quarters, making them very rare.

Looking for the 1970 S Washington Proof Quarter Error - Meridian Coin

 

[against the wind]

I read that article by Meridian Coins.
It never explained why 1941 Silver Canadian Quarters were in the San Francisco Mint in the first place.
Interesting article.