Two new postal cards appeared on 1 October 1945, in the aftermath of World War 2 --- a 75c card and a 2.00-franc card. They remain underappreciated despite offering the specialist a trove of interesting post-war rates, uses, and cancels.
Here are three unusual uprated uses of the 75c card.
Uprated in 1950 For Domestic Use

Remich to Mondorf-les-Bains
22 Jun 1950
The 75c domestic rate was increased
to 1.00-franc on 1 Jan 1949.

Printed Back
Jean Maroldt, Notary
Remich
Uprated in 1946 for Use to France

Larochette (Belgian-style cancel) to Strassbourg, France
19 June 1946
Although the postal card rate to France was set at 1.50-franc as of 20 Feb 1945, a new card was not issued for this rate in 1945.

Uprated in 1946 for Special Delivery to Belgium

Luxembourg-Ville to Brussels, Belgium
4 Jan 1946
Uprated 7.00 francs to pay the special delivery fee!
