Try to convice any mail room to shake down the envelopes and slit along the bottom edge. I tried that once and lost. LOL
From the "postal histoey" aspect, I would retain it as an example of the Saint-Nicolas machine cancel, which has appeal to topical collectors. Who knows, it might be an early of late date of use of that particular slogan cancel there?
Sorry, not Canadian examples, but here are two envelopes I saved for their Universal Model-K machine cancels, typically from small to intermediate-sized offices. The first from Clay Center, Kansas, was cut across the top of the stamp, but from the era when many of these machines were being phased-out of use across the U.S. The quality of the cancel was too nice to discard.

And even worse yet, from Eureka, Kansas, but which serves as possible date-of-use data.

Everything is collected by someone!