Swiss Soldier Stamps
According to the site, "The first of these Swiss soldier stamps were designed in 1915 with two different motifs, and were really intended just to be souvenirs for the soldiers. Then in 1916, stamps that were cancelled on envelopes were sold to provide money to help support Swiss soldiers and their families who were in a financial crisis over the long period of time the soldiers were on alert for invasion. Swiss stamp dealers recognized the value in these small circulation stamps, and profited from them."
It goes on to say, "Because Swiss soldier stamps were issued by the regiment or individual company and not good for mail in general, they were then classified as charity stamps. In 1939, many Swiss units began issuing soldier stamps, with many of them being overprints of the original WWI stamps. They had official approval to print stamps, and even though the Swiss mail had to approve each issuance, they didn’t recognize them as valid postage outside of military use."
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