This unique Canadian 50¢ dated 1970 is struck on a 72% silver and 28% copper off-metal planchet (should have been nickel). It was authenticated and certified MS 64 PL by NGC. It is the only one known after almost 50 years.
There are 3 known 1970 Canada 50¢ off-metals struck in silver instead of nickel and all have been certified by PCGS. One sold in a 2007 Heritage auction for $3,450. Another sold in a 2017 Heritage auction for $3,760. The third known silver example is in a private collection. All three inserts say "Struck on Silver Planchet."
This discovery coin (72% silver, 28% copper) is most likely an intentional mint error since it does not match any coins being struck during 1970 at the Royal Canadian Mint. A fascinating unique major mint error!
Off-Metal Errors are featured in chapter 29 of the
NLG award winning book, World's Greatest Mint Errors.