Unusual World War 1 Patriotic War Effort Fundraising Postcards

I was at Denny Peoples' house over the weekend and he had these two identical postcards that, while not in my wheelhouse, were just unusual and interesting enough that I couldn't not buy them.

They are postmarked July 2, 1918 in San Francisco, California. Dimensions are 7-3/8" x 6-1/8" in size. The obverse is a printing of the scene of signing of the Declaration of Independence, with the message in Old English font:







The reverse is where they really get interesting...

Both are addressed to "Secretary McAdoo, California, via P.O. Sacramenta, Cal" with one of them modified in pencil to "Washington DC".

Both are franked with a 2-cent Washington at top right.

There is a printed message, again in Old English font:




and a signature line.

Beneath that is a ruled box with the following instruction:

"PLACE GIFT OF POSTAGE STAMPS HERE (1C to $5.00) AND CANCEL BY SIGNING YOUR NAME ACROSS THEIR FACE"

The first card has seven 10-cent Franklins affixed, with the manuscript cancel "COMPLIMENTS OF SAN FRANCISCO CALIF" written across the seven stamps.




The second card has a more colorful selection of stamps, with incredibly meticulous handwriting stating:

"And as Americans let us in all loyalty give service to our country untill success."




These appear to be voluntary donations to the war effort (at this time the USPS was funded by the Department of the Treasury), as the stamps were purchased, and then voluntarily canceled without redeeming the services for which they were purchased, hence a donation.

The "Secretary McAdoo" to whom they are addressed was William Gibbs McAdoo, who served as U.S. Secretary of the Treasury from 1913 to 1918.

A couple of comments:

1. Cancels like this would *COMPLETELY* lose all context once soaked from the postcards; they would make no sense whatsoever.

2. How would you classify the usage of these stamps? It is not a postal use. It is not a revenue use. It is a voluntary voiding of the stamps.

It's really a semi-postal type of usage, perhaps with a bit of a philatelic inspiration. And the catalog numbers are correct, although it would have been better to leave them off the document since they are obvious (perf 11) Interesting items; I have never seen anything like this before.