What or Who was Wilson & Company of Pittsburgh, PA?

In August 2023, a seller on Ebay posted a couple of lots that looked like this:

An intriguing group of plate number singles...all the stamps are canceled with a Wilson & Co. circular date stamp, all neatly in red, and with an absence of other stray marks.  All the stamps are preserved margin copies with plate numbers.  Seems like a 1898 era philatelist might have been at work making these. For those that collect the dollar value 1898 stamps, these cancels are not strange to us, and they appear with some frequency, even on high value items:

 

Wilson & Company cancels on R160 plate strip sold in a 2008 Spink auction.  Image available at Stamp Auction Network.

I've managed to accumulate a few examples with the Wilson cancels:

Even a scarce R159 with the overprint reading down:

All of my examples, including a fourth not shown here, have no gum, but are all in great condition except for three knife cuts on the R159.  It seems likely that the maker of these cancels was involved with the Pittsburgh stock exchange, and was also a stamp collector.  A bit of research proved the latter:

from The Philatelic West Camera News of August 1903, showing a Mr. H. E. Wilson as Twin City Philatelic Society's "Counterfeit Detector".  Maybe the ARA needs a new position with the same name?  

It can be established that the H. E. Wilson listed as the Counterfeit Detector is the maker of the cancels on the stamps above through an example of a letter he wrote that is available online, that has the cancel he used on the stamps in the upper left of the envelope, using a similar, if not the same color used to cancel the stamps:

The enclosed letter:

Wilson & Co. and H. E. Wilson are not listed as members of the Pittsburgh stock exchange in 1901.  Somehow Mr. Wilson's activities, professional or through private association, brought him into contact with dollar value 1898 stamps, and somehow his company's handstamp device was likely legitimately used.   His office building, the Fitzsimons Building, was located at 331 Fourth Avenue, in the heart of the Pittsurgh financial district.  The stock exchange itself was located at 340 Fourth Avenue, across the street from H. E. Wilson's office.

The biggest lesson from this story is that the apparently scarce and valuable plate singles and plate strips that are in collections and on occasion sold at auction are in part philatelically inspired, though likely used legimately by a collector with a professional reason to use these high value stamps.