Ceylon: Postage Due Aerogramme

Ceylon air letter (Wiegand #12a - white paper, no watermark, “Fold here …” on sealing flap is 58.0 mm wide) sent from JAFFNA (10 MY 55) to Tours, France.

Postage due calculation in the country of origin
The 20 ct aerogramme was taxed as short paid, because the aerogramme rate to France was 40 ct. So double the deficiency (40 ct) was postage due. The standard conversion rate should have been 20 UPU ctms = 35 ct (1 ct = 0.8 UPU ctms). Ceylon made use of the opt-out clause, which was agreed upon at the 1952 Brussels UPU congress, and calculated with, roughly, a 15% reduction in letter rates: 1 ct = 0.68 UPU ctms, so 20 UPU ctms ≈ 30 ct.

Postage due calculation in the country of destination
In France the standard conversion rate should have been 30 f = 20 UPU ctms 
(1 f = ⅔ UPU cmts). However, also the French postal authorities made use of the opt-out clause converting 27 UPU cmts into 31 f (1 f = 0.871 UPU ctms leading to 20 UPU ctms ≈ 23 f), equivalent to roughly a 20 % decrease in letter rate, Four postage due stamps with a total face value of 31 f document that the postage due has been paid.


Reference:
Wiegand, Katalog der Aerogramme von Asien, 2000