Good questions. Good observations. At the moment, you may be convinced it is a former Canadian Ranger No. 4, but without some more evidence, would have a difficult time convincing another person?? I think in the art world they call it "provenance" - some sort of documented evidence to support the story or history of the piece, over and above some person's "say-so". And, as you say, the serial number matched accessories would go a long ways towards that!!! I see pretty suspect examples of No. 4's - mixed woods, mixed or missing parts, mixed era components, offered for sale at $500-$600 - I do not know what they actually do sell for, but would think a properly documented one would be double or triple that to an interested buyer?
From what I have read, a Canadian Ranger No. 4 could be anything from a WWII or earlier veteran that has been patched and fixed no end of times, all the way to a fully matching "Irish Contract" Mk. II. I understand that Canadian DOD was going to commercial market to buy some parts to keep some of the older ones functioning...