This is the first year of issue and it is housed in a brand new, blemish free slab. It is rare to get a grade higher than MS-66 on these coins.
The mint didn't strike, package or distribute them with MS-70 quality coins in mind. The Royal Canadian mint didn't really get their act together until the 2010s, and even then, their bullion was plagued with issues. A lot of these coins banged together in drawers and the soft metal was damaged.This can take multiple grades off a coin. Nobody ever really took care of them thinking nobody would ever collect them. The discerning collector of modern Canadian pieces knows just how rare coins like this are.