Ther really SHOULD be some "wriggle room" available.
It was even ADMITTED on several occasions that the RCMP, when they were looking after things, had LOST more than 30,000 registered guns. Another figure which made the newspapers was 65,000 LOST, right in the Registry.... and that all was BEFORE the New Brunswick silliness of applications being shredded because they hired the wrong people to do the job. Their own figures say that roughly a QUARTER of the Restricteds in the country have been lost, one way or another........ and, when this one came to Canada, there was only Registration and NO classes. ENTIRELY possible that it was registered in 1945 or 1946 and the records have been lost...... or flushed..... or shredded.... or overlooked..... or ignored.
They even lost one of mine, back in the late 1970s: I had had my 1911 Steyr..... WITH a carry permit..... for THREE YEARS including a change of Provinces, all legal and on paper, when they audited the dealer I bought it from...... who had proof of where he had shipped it..... then came after ME for "Unregisterd Restricted Weapon".
Fortunately, I HAD all the paperwork..... every single piece of it: permit to ship it from North Van to Lewisporte RCMP, Application for Registration, permit to take it home to Job's Cove, Certificate of Registration FROM OTTAWA, range permit every year, permit to drive to Manitoba with it, permit to take it to the range in Manitoba...... every year. If they had bothered to cross-check their own records, they would have found the error, but it's a lot more fun to threaten someone who has done EVERYTHING right.
If I had been in the "Armed Robbery" business I would not have had to do ANY of this paperwork, I would have been put to NO inconvenience, I would NOT have been threatened NOR treated like a Criminal (or worse: Criminals get the benefit of the doubt where mere "Taxpayers" do not). If I sound like a crank, it is because I have had it PROVED to me that my country treats honest Citizens worse than it treats Criminals.
Be safe, friend.