Panama 1975-76 Coinage at Royal Canadian Mint

Why is this listed as a "Mule" in the Numista catalog?

https://en.numista.com/catalogue/pieces70444.html

RCM used the dies provided by the Panamian government, and removed the FM mintmark, but did not remove the "Ley .925" indication that the coins were Sterling silver. (The coins are copper-nickel.) It is an error, but is it really a mule (mismatched dies)?

Also, there was a similar error for the 5 balboas coins for 1975 and 1976. 4,000 were minted in 1975 and 5,000 in 1976. This does not appear to be in the Numista catalog.

http://www.elfreeman2.com/11f/11f373r.jpg