As with so many other things I come across, I really wish these were still on the original document, as context is everything. What makes this Scott #14 strip of 3 especially unusual is that they were used as revenues a full 6 years after being demonetized (no longer valid for postage).
The second, more serious, demonetization was prompted by the outbreak of the American Civil War in 1861. Southern post offices held substantial U.S. assets in the form of their stamp stocks, and the Confederates could theoretically have brought in some income by selling those stamps to private individuals in the North.
In April 1861, John H. Reagan, postmaster of the CSA, ordered the offices in his charge to return their stamps to Washington D.C., however few seem to have done so, and by June 1861 U.S. postmaster-general Montgomery Blair ordered the severance of postal ties and the production of new stamps.
In August the stamps of the U.S. 1861 issue began to be distributed throughout the Union, along with orders that postmasters should offer to exchange old stamps for new for a period of six days after giving “public notice through the newspapers and otherwise”. After the six-day period was over, that post office was not to recognize the old stamps as paying postage.
In addition, postmasters were to accept letters with old stamps from other post offices until set dates, ranging from September 10 in the East, to November 1 from letters arriving from the Far West. (Later the periods were extended for an additional two months.) The process stretched over some months; the large cities in the East were exchanging stamps in the third week of August, while some small remote offices did not start until November. General confusion, combined with exhaustion of the new stamps at some post offices, led to some instances of the old stamps still being accepted on letters after demonetization, although surviving covers are rare.
I suppose it’s possible that six years later someone said “well, I can’t use them for postage anymore, so I might as well use them for something else.”
I’ve seen a few examples of demonetized postage used as revenues in The American Revenuer and in auction archives, but this is only the second example I have seen in person.
It definitely has some faults, but on an item like this condition is somewhat meaningless as I’m unlikely to ever see another example.