Am I correct in assuming that silver coins pretty much disappeared from
circulation in Canada in the 1960s, as they did here in the U.S.?

Yes, but a few years later. The last 90% silver US coins for circulation were
minted in 1964, but Canada continued to mint 80% silver coins until 1967. In
1967 some Canadian coins were minted in 50% silver as well as 80%, and some
1968 coins were minted in 50% silver as well as nickel.