Each of the ten Caritas semi-postal sets issued between 1930 and 1939 contained a one-franc denomination. What common rates did this denomination serve? From December 1, 1929 to October 1, 1940, only two:
- (i) the 1-franc UPU post and postal card rate; and
- (ii) the 1-franc second step postage rate for UPU surface
letters weighing from 20 to 40 grams.
Although philatelic uses of these Caritas semi-postal issues abound, finding a cover or card with any of the 1-franc denominations used to pay either of these two postal rates is very challenging. Here is the only example in my extensive Luxembourg semi-postal collection!
20-40 g UPU registered letter
Luxembourg-Ville, January 9, 1931, to Lucerne, Switzerland
1.75 F postage + 1.75 F registry fee + 1 F second step postage