If we are talking chests we have to realize that there would have been over 20,000 Cno7 chests made, and so the contracts could have been shared. I think I have only spotter two variations to the manufacturer on the Cno7 chests. There were one or two modifications to the chests, so some may have had their mods, and some may not have. I have about 20 or so in the shed now, but in all honesty I have not examined each and every one. I have only had two of the Canadian no15 chests (they were mixed in with Cno7 chests at my source for them) but I also have 300 or so Bren chests. There is some minor variations to ththe Bren chests as well.
The no15 chests in Canada would have been much smaller numbers, likely around 1500 or so. But they did come in batches, so there may ave been allowances for what the various manufacturers could do.
But in the end, the number of hinge holes (3 for Brit and 4 for Cdn) seems to be the best indicator as to country of origin.