Help With Information On 1911 KeVII Covers

Maybe I'm not looking hard enough, but I can't find many covers with the Harrison 15x14 perforations, despite there being plenty of used examples available online. Is there a reason for this?

Here is an SG285 (149) I picked up in an antique store that I really like. I couldn't imagine washing it off and potentially hurting it's color, which is known to be a problem for this series.
Would this be considered a scarce item, or just something GB collectors don't really bother with?

Edward VII

Thank you! Haven't had my coffee yet.

It's also 1912. [The cover, not the stamp.]

That's a busy little cover. It has some eye appeal.

The stamp itself is poorly centered, so (in my opinion) it's living its best life, as the kids say, right where it sits.

Is the 2nd 1 Oct backstamp Portadown?

SG Concise 2025's price for the cover is four times the price for the used stamp.

It's a very nice cover. Tandragee to Portadown to Philadelphia to Reading, all clearly enough dated to show the cover's journey. And it's quite a late use of the stamp, because the George V equivalent was issued on October 9th, while the cover was in transit.

Excellent! I did not notice the Portadown before. Off-centered gb stamps do not bother me as much. I barely notice them. They're overall neater, better produced than let's say classic US stamps, where sometimes half the design is cut off!
Thank you for the comments.