The BNA Topics Journal, Whole Number 561, Volume 76, Number 4 (2019 fourth quarter) has an article by Tom Meyerhof entitled "The Canadian Multipost Co Ltd".
He explains that this company manufactured and sold to large mailers, 'stamp affixers,' which used coils of 500 stamps aligned sideways. Between 1912 and 1914, the
Canada Post Office Department printed King Edward VII 500 stamp rolls in 1 cent green, 2 cent carmine and 2 Cent green denominations in both sideise and endwise positions.
On January 1, 1920, the Department issued the unpopular endwise stock of 3,000 1 cent and 2 cent rolls to major post offices to sale as normal stamps. No date was given as to when the production of sidewise rolls was stopped or if they were also supplied to post offices. During production, perforations were changed from 8 to 12 and thinner, but equally strong, paper was used as the original perforation and paper did not tear well at the perforations.
The original perforation and paper was OK with the 'stamp affixers' machines as they employed a guillotine action to separate stamps.
Post Offices were using the Canadian made Multipost stamp affixers which guillotined the stamps, regardless of perforation size.
Based on this article, perhaps bwdavis' stamps are from a roll provided to a major post office, which would explain the differences we are seeing with his trio of stamps. Having a margin on the far right suggests these three stamps may be numbers 498, 499 and 500 of the roll.