Here is a delightful Swiss UPU formula postcard with a miniature envelope affixed to the message side, replete with a heart, four-leaf clover, mushroom, and an elf announcing:
Ein Brieflein bring ich Dir / Drum freue Dich mit mir!
The 'postcard' was posted at Larochette in the Grand Duchy, November 25, 1901, to Esnes (Meuse) in the French Lorraine near Verdun, with a 10c Adolphe definitive paying the ten-centime UPU postcard rate. But because the card carried the Lilliputian envelope and its contents, it was not accepted at the UPU postcard rate.
In Luxembourg or, more likely, in transit on the Longwy a Charleville Railway Post Office a tax mark [‘T’ in a triangle] and a rectangular boxed ‘Affranchissement Insuffisant’ auxiliary mark were applied.
The miniature envelope itself bears the Gare de Longwy [?] backstamp of November 26th! And on the address side, a pair of
10-centime French postage due labels postmarked Esnes, Meuse, November 26th, documents payment of the tax.
But how was the penalty calculated? The UPU 15-g letter rate was 25c. Doubling the 15c deficiency would result in a tax of 30c. Perhaps the 10c paid by the sender was deducted from the 30c figure? Suggestions?
Oh, and here’s the letter that was in the little envelope!