1917 US Cover RARE Postally Used non-approved WAR STAMP overprint #481

Description

Unique?  At least only example I can find of a postally used U.S. WAR STAMP overprint on #481 (see story below).  An eBayer recently shared 2 War Stamp Covers with #482 which he said wasn't cheap.  The background on this cover (below) makes it a cool story.
I have a family collection of +1000  covers which most likely have marginal value.  However, occasionally you stumble on one that deserves attention.  At first, this cover appears to be a strip of 3 unperforated US Stamps #481.  On closer inspection, the middle stamp has 'WAR STAMP' overprint.  No big deal...until I determined the Bureau of Engraving and Printing never issued any war stamps.
In 1916 in order to help finance the war effort, postal stamps were taxed primarily within the British Empire by overprinting the stamps with the words 'WAR TAX', 'WAR STAMP' and various derivations.  There was some thought by members of the American public that this practice should be applied to US postage stamps and several examples (one of which is the middle stamp on this cover) were submitted to the Bureau for consideration.
The idea was rejected and the US did not issue any war stamps.
HOWEVER, (at least) one example  escaped and was used postally on an envelope from E.F. Pope in Colmesneil, Texas to Charles S. Thompson in Los Angeles.  The envelope was never opened because there was no correspondence inside.  The only objective was to use a stamp that had not been approved for postal use and send to an infamous early 20th Century stamp collector/dealer.
Bios below lifted from internet:
Sender:  Edmond Floyd Pope
(1870–1952) collected birds’ eggs in Texas and other locations from the mid-1880s through the late 1920s. He was also an inspector for the predatory animal control division of the United States Biological Survey, a master craftsman of the longbow, and a breeder of flying squirrels for the pet market. Several of Pope’s egg records have been questioned in recent years. He is, however, still considered to have been an expert in the manufacture of the longbow.
Recipient:  THOMPSON, Charles Sidney
(1881-1960) was born on January 6, 1881 in Canada. He became a collector, amateur ornithologist, stamp dealer, author, printer, teacher, and museum curator.
In November 1901, while attending Stanford University, Thompson authored a note in Condor on the
Notes on San Luis Obispo County Birds
. He was appointed secretary of the Cooper Ornithological Club in November 1903 at the Northern California chapter meeting due to the resignation of Mr. Kaeding. In 1905 Thompson received his degree in zoology at Stanford University. He became a teacher in Los Angeles schools, and in 1914 was hired by the newly opened Southwest Museum under the directorship of Frenchman, Dr. Hector Alliott as assistant curator of ornithology. By 1916 Thompson had become curator of economic and field ornithology at the Southwest Museum.
Thompson was also a member of the American Philatelic Society, the American Stamp Dealers Association, and the Metropolitan Philatelic Association. He was president of the International Philatelic Association. He called himself a general collector. His specialties included stamps of Austria to 1910, and an expert on stamps of Albania, Bosnia and Crete. He also had a large collection of sea shells and "ornithological specimens of all kinds, of which we have some ten or twelve thousand specimens in two buildings erected for the purpose." He also collected prints of birds and books related to ornithology, ethnology and anthropology.
1910 Census:
Charles Sidney Thompson = Alma Victoria Hand (1884-1947)
1. Charlotte Victoria Thompson (1909- )
Since 1923, Thompson has been the prime suspect in the philatelic world of the famous forgery of Hawaiian Missionary stamps of 1851 that a man named George Grinnell sold to New York stamp dealer, John Klemann in 1919. He had become a stamp dealer in Los Angeles by that time, and he wrote for
Philatelic Gossip
and
Mekeel's Weekly Stamp News
. By 1924, Thompson, of Los Angeles, was a member of the "nameless" [stamp] Collectors' Club of Orange County.
In the 1930 census he is listed as a stamp dealer.
In March of 1941, Thompson moved from Los Angeles to Holton, Kansas, where he became editor of
Weekly Philatelic Gossip
, one of the most important and respected stamp magazines of that era. Thompson returned to California in September 1943.
The Southwest Museum contained the Charles Sidney Thompson collection and library of ornithology, with 18,000 specimens. Presumably they now rest with the Autry Museum of the American West.
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It appears both EF Pope and Charles Thompson were bird lovers and stamp enthusiasts.  There paths must have crossed sometime before the date of this cover in 1917.
Cover has natural age discoloration and left edge has some wrinkling (not creases).