Understanding the Luxembourg-Belgian Airmail Mixed Frankings after Luxembourg’s 1935 Currency Devaluation (April 1935-May 1939)

I. Background

Kind readers of this blog have pointed out that on or about April 1, 1935, the Belgian franc was devalued 28% with respect to the Luxembourg franc, with one Luxembourg franc now worth ~1.25 of the devalued Belgian francs. It was at this time that Luxembourg and Belgian departed from the gold standard.  This exchange differential remained in effect until the World War II German occupation in 1940.
 

Consequently, when analyzing airmail covers with Belgian airmail supplements during the devaluation period (from 1935 to May 1, 1939, when foreign supplements were no longer required), the postal historian must adjust the required Belgian airmail supplement upward to reflect Luxembourg’s now comparatively stronger currency. 

For example, if the pre-1935 Belgian airmail supplement was one Belgian franc, in 1935 it necessarily increased to ~1.25 Belgian francs to take into account the devaluation of the Belgian franc vis-a-vis the Luxembourg franc.  But keep in mind that the Belgian stamps were only available at the main post office in Luxembourg-Ville, and that apparently the lowest denomination available for mixed-franking of airmail was the Belgian 50-centime stamp.

At page 165, the Basien-Hoffkamp rate book provides conversions of the Luxembourg franc vis-a-vis the Belgian franc, German mark, and French franc, citing Luxembourg Post-Instruction No. 1046/19 and No. 1074/20.

In the chart below, I’ve simplified the arithmetic:

Airmail Supplement in francs: 1933 to 1 May 1939 (see Basien-Hoffkamp, Luftposttarife 2, pp. 171-172)	Airmail Supplement Adjusted for the 1935 Devaluation
0.25	~0.31
0.50	~0.63
1.00	1.25
1.25	~1.56
1.50	~1.88
1.75	~2.19
2.00	2.50

II. Examples

Here are a few examples:

Luxembourg-Ville to
Bayenga-Wamba, Belgian Congo 3 Sep 1935 
 (routed “Via Londres-Juba”)

20g letter rate to the Belgian Congo = 1.50 LFr

Airmail Supplement = 3.00 Fr/5g

Adjusted upward for 1935 devaluation = 3.75 Fr/5g

Rounded to 3.50 BFr → 3.50 BFr paid
(no Belgian 25c stamps available)

Luxembourg-Ville to Johannesburg, South Africa 31 Mar 1936 UPU postal card rate = 1.00 LFr Airmail Supplement = 3.50 LFr/5g Adjusted upward for 1935 devaluation =  ~4.38 Fr/5g Rounded up to 4.50 BFr →  4.50 BFr paid

Wecker to Cape Town, South Africa 9 Sep 1936 20g-40g UPU letter rate = 2.75 LFr UPU registry fee = 1.75 LFr Airmail Supplement = 3.50 Fr/5g x 5 [21g letter] = 17.50 Fr Adjusted upward for 1935 devaluation =  ~21.88 Fr/20-25g Rounded up to 22.00 BFr → 22.50 BFr paid → overpaid 50c

Luxembourg-Ville to Pittsburgh, PA USA 13 Mar 1937 UPU 20g letter rate = 1.75 LFr Airmail Supplement = 2.00 Fr/10g x 3 [?] = 6.00 Fr./20-30g Adjusted upward for 1935 devaluation = 7.50 Fr/20-30g Rounded up to 8.00 BFr → 8.00 BFr paid

Luxembourg-Ville to the Persian Gulf 6 Aug 1937 UPU 20g letter rate = 1.75 LFr Airmail Supplement = 2.50 Fr/5g x 4 [?]= 10.00 Fr/15-20g Adjusted upward for 1935 devaluation = 12.50 Fr/15g-20g Rounded down to 12.00 BFr → 12.00 BFr paid

Luxembourg-Ville to Johannesburg, South Africa 16 Aug 1938 UPU postal card rate = 1.00 LFr Airmail supplement = 3.50 Fr/5g Adjusted upward for 1935 devaluation = ~4.38 Fr/5g Rounded up to 4.50 BFr → 4.50 BFr paid

Luxembourg-Gare to Colombo, Ceylon 21 Nov 1938 UPU 20g letter rate = 1.75 LFr Airmail Supplement = 2.50 Fr/5g x 2 [?] = 5.00 Fr Adjusted upward for 1935 devaluation = 6.25 Fr/5-10g Rounded up to 7.00 BFr → 7.00 BFr paid

III. Airmail within Europe after the 1935 Devaluation

At page 171 (Luftposttarife 2-1), Basien-Hoffkamp lists the 20g airmail supplement as 50c for Belgium, Germany, France, Great Britain, the Netherlands, and Switzerland, and 1.50 F for other European countries.

Here more research and a census would be helpful.  Was the 50c tariff rounded up to 1.00 F?  Was the 1.50 F tariff rounded up to 2.00 F? Some of my covers to the 50c-tariff countries have 50c franking; others, however, have 1.00 F franking.  And I also have covers with 50c franking to European countries other than those that Basien and Hoffkamp list.

Luxembourg-Ville to London, England 5 Feb 1940 UPU 20g letter rate = 1.75 LFr Airmail supplement = 50c

IV.  Is additional information available from the UPU Library?

Robert E. Picirilli, writing in his 226-page study entitled Postal and Airmail Rates in France & Colonies 1920-1945 [France and Colonies Philiatelic Society, 2011], states that the Universal Postal Union periodically published a Liste générale des services aéropostaux (referred to as the “AV1 Liste”), which for Picirilli proved “to be a valuable source of information, often confirming and sometimes adding to what [he] found in the official journals.”  And he says that the UPU librarian, Solange Avila, was of great assistance in tracking down the UPU records of French airmail rates.

We might consider doing the same in the hope of further expanding our knowledge of the pre-WWII airmail rates.

V.  Keep your comments coming!

I’m grateful to my European collector-colleagues for their incisive comments and interest in this blog.