this is an article i wrote in german as well, here is now a translation and explanation for english and american speakers and NZ enthusiasts.
In the german publication "Krupp-Kraftwagen im Kriege" from the series "Waffen-Arsenal" by Podzun-Pallas Nr. 107, Page 26 i found the statement that the number combinations on german number plates for official organs like Wehrmacht, Luftwaffe, Kriegsmarine, Police and Party Organs are belonging to a specific region, the "Wehrkreis" ("Defense area"). This "Wehrkreis" is a region where the recruiting and commandment of german troops is controlled and supervised by a "Wehrkreiskommando"(Defense area command). There were several of this regions and commands in Germany.
They were numbered from 1 up to 21 with roman numbers. (According to a chart of summer 1941)
You will find this regional numbers on the number plates of national german organs, like the Wehrmacht.
When the "Wehrkreis" has a number from 1 to 9, the numberplate has 5 numbers and the first one is the "Wehrkreis".
When the "Wehrkreis" has a number from 10 to 21, the numberplate has 6 numbers and the first two are the "Wehrkreis".
There may be some number plates with less or more numbers due to the changing grade of motorization of the german armed forces, but in most cases you will find the combination mentioned above on historic images.
This not only allows you to identify the home garrison on pictures, it is also necessary for the original look of your bike!
E.g.: If you drive a NZ marked with the insignia of the german paratroop regiment "General Goering" which was originally in barracks near Berlin, you should fix a number plate with the combination:
WL-3XXXX
If you drive a NZ marked with the insignia of the "LAH" which home garrison were in Leipzig, you should fix a number plate with the combination:
XX-4XXXX (The first two signs are not allowed in Germany)
German mountain troops may have the numbers
WH-7XXXX or WH-17XXXX
belonging to their home garrison either in Bavaria or Austria(Ostmark)
All german navy forces need
WM-10XXXX
Heres a list to help you find your matching region:
1 - Eastern Prussia (Ostpreussen)
2 - Stettin and Pommerania
3 - Prussia
4 - Saxony
5 - Wuerttemberg-Hohenzollern and Wuerttemberg-Baden
6 - Rhineland and Westphalia
7 - Southern Bavaria
8 - Schlesien(Silesia)
9 - Hessen
10- Nordmark and the german coast(Schleswig-Holstein, Hamburg and the northern part of Niedersachsen and Mecklenburg)
11- Hanover (Niedersachsen)
12- Rheinland-Pfalz and Saarland
13- Northern Bavaria and Nuremberg
14 to 16: Not assigned
17- Northern Austria (Ostmark)
18- Southern Austria (Ostmark)
19- Not assigned
20- Western Prussia and Danzig
21- Posen and Reichsgau Wartheland
You will find an image attached where all areas are listed (Summer 1941):
