ViccyVFU wrote: ↑
13 Sep 2021 22:26
The point being that whether its scissor OR guillotine cut, I can perform both of those actions on my desk today, and no one could age it.
You certainly could, so to go all Sherlock Holmes on you: Why would you?
To do it at home would be almost motiveless and a sign of a very strange mind to wake up one morning and think "I know, I'll just trim that pair of joined stamps with my scissors". Nothing to gain by doing it and nothing to lose either except a little bit of time and a little bit of your remaining sanity!
But for a Postmaster or clerk to do it is a different matter entirely. We know the strips of stamps were made manually for use as coils in vending machines. We know how sensitive those mechanical machines were, so if the joined pair were not joined absolutely straight, it would be sensible, logical and necessary to trim to fit, preventing jams or blockages in the machine, preventing customer dissatisfaction if it happened and a small investment in office time to save wasted office time later in rectifying the avoidable fault.
The third possibility is to defraud collectors. As has been said, creating these coil pairs is a simple matter and proving when and by whom is, indeed very difficult. But, would a "forger" go to the bother of trimming them? I think they'd more likely leave them uneven in the hope nobody would notice.
Weighing up the evidence, the Postmaster / clerk scenario is the elementary answer!