The mystery:

Why do we see perfins on coil stamps?

Multi-die perforators are quite effective at perforating sheets of stamps. However, they are not very good at perforating single stamps or single rows of stamps. Of course, you could turn a row of stamps sideways and perforate them one at a time, but this is not a very reasonable thing to do. Any resonable person would just get a sheet of stamps and use the perforator as it was designed.

The mystery deepens:

Here is a cover that has a coil stamp. Notice the cancellations.

At 8:30 p.m. on Nov. 15, this cover was cancelled at a post office sorting station. The following day this cover was cancelled again at the Legislative Assembly. As you can see from the back of the cover, this happened by 8:00 a.m.

It appears that the Legislative Assembly mail room put insufficient postage on this letter, retrieved it, then added the required postage and cancelled it by hand. They then applied a cancellation to the back of the envelope to establish the time this happened.

Canadian Companies Using Coil Stamps for Perfins