The late John Robertson told me a number of times that he was told by a senior armourer he knew that at one time after WWII the Canadian stores system policy was to scrap MkI rifles when they came through workshops and replace the receiver with what was then the Canadian Army standard, the MkI*. A policy in reverse of that would have been a much better idea IMHO, but nevertheless that was John's statement. It could be that this was just the policy at one workshop, or even of one OIC (Non-commissioned or otherwise) perhaps, but there it is. He never claimed that statement was confirmed by any other armourer of that vintage, and the one or two I have spoken to did not know of it. However, in this large country of ours with different military districts etc. I would not be surprised if different policies prevailed, or if those in command of workshops made their own policies at times.
Since you have there a nice MkI trigger guard, you might have what is left of the rifle after a receiver swap was done, but those numbers are not stamped in the font I have seen used to renumber rifles in the post-war period. Like many others, I dislike the fabricated trigger guards and whoever built this rifle might well have preferred the solid forged type. We know there were plenty of spares at SAL and that building up rifles was not uncommon at all. As I've recounted before I was told by a former Lt. Cmdr. of WWII vintage who was an technical inspector for DND postwar, that he had a rifle built up as a gift for a retiring colleague and there was nothing uncommon about doing so. The rifle even came with the tag on the barrel he said, and it was built up, not removed from stores, he was quite specific about that.
As has been mentioned, there were lots of un-numbered 1955 receivers floating around, and lots without even the last digit, which you will see is probably separately stamped(?)
If I had to guess I'd say it is a made up rifle. No.4 parts were so plentiful even in to the 60s and 70s that many of the DCRA and ex-servicemen shooters had large stocks of the stuff. The maple forend was considered preferable for target rifles, but not liked by soldiers or armourers, so I have been told by some who were such at that time.
The safety has been reshaped to better clear the PH sight which of course was not designed to clear the Canadian "lady slipper" safety.
Didn't read the whole thread, but did just see your post about the five digit number: definitely an out-of-service build then IMHO.
