Nigel
I have had a look at the website
http://www.PhilaSeiten.deand found the discussion on German Exchange control.
While most of this touches on 1918-1925, mention is made of 1933-1939
for which a booklet exists by KH Riemer with title
Devisenkontrolle im Auslandsbrief- und Paketverkehr im Deutschen Reich
1933 bis 1939
published by Poststempelgilde Rhein-Donau as Heft 93 in 1983.
There was another period of exchange control from 1948 to about 1955
about which little is recorded. I might write something when I have done
the 1918-1925 stuff.
TomWolf_de is correct with the law of 15 Nov 1918 signed by Ebert and
Haase. The list of offices and numbering is correct. There were other
offices which were never numbered which closed in 1919 plus an office at
Hindenburg which was open in 1923 but little is known of this.
Friedrichshafen (office 21) used Stuttgart (office 19) labels. I have
never seen labels with the number 21.
Labels with numbers 25 (Cleve), 26 (Aachen) and 27 (Trier) do exist but
the offices at Aachen and Trier in occupied Rhineland were not allowed
to open by the Belgians and the French. So labels 26 and 27 were used up
in Hamburg and Muenchen.
Exchange control ceased for unregistered and registered mail in October
1920 but was soon re-imposed on registered mail. This reduced the amount
of mail needing inspection and so you will find labels intended for one
office used somewhere else.
eg Elbing (office 23) used labels for Konstanz (office 12) overprinted 23
Dresden (office 4) used labels for Elbing overstruck 4 including the
Konstanz ones already overprinted 23. Dresden also used Bremen (office
2) labels usually with a 2 line Postueberwachungsstelle cachet.
Emmerich (office 6) used labels from Freiburg (office 9) with number
altered in manuscript in 1919 - this may have been an error of
distribution by the Zentrale fuer Postueberwachung who printed and
distributed the labels in 1919 and 1920.
Hamburg (office 10) used labels from Lauenburg (office 22) and Aachen
(office 26) sometimes but not always overstamped 10 in a ring.
Muenchen (office 16) used labels from Bremen (office 2), Emmerich
(office 6), Karlsruhe (office 11), Stuttgart (office 19), Aachen (office
26), Trier (office 27). Sometimes these were overstruck 16 but not
always however the label is usually struck with the circular (30mm dia)
Muenchen arms type cachet.
The 1818 error for 1918 is illustrated. I have 1818 labels from Berlin
(office 1), Bremen (office 2 but overprinted 16 and used at Muenchen),
Breslau (office 3), Dresden (office 4), Frankfurt (office 8), Freiburg
(office 9), Hamburg (office 10),
and have been told about 1818 labels from Koenigsberg (office 13).
An adapted wartime label from Stuttgart is illustrated by TomWolf_de. I
expect many more adapted labels and cachets are in people's collections
unrecognised. The circular Freigegeben St. cachet must be from
Stuttgart. It is very common.
The parcel card dated 17 MAI 21 with a Stuttgart re-direction label is
unusual. There were at least two printings of the label with the capital
letter of Muenchen the most obvious difference. There was a third label
without Muenchen 3 Bhf and two different printings with Hamburg 7
replacing Muenchen 3 Bhf where the H of Hamburg is the most obvious
difference.
Only insured parcels went through the Exchange Control and this ceased
in August 1921 when the Customs were given the job of checking Exchange
Control regulations at the same time as they checked Customs regulations
(why this did not happen at the start I do not understand as it seems
daft to have two different Government Departments check the same parcel).
Hope this helps
Robin