Hello Kostas,
According to the factory ledgers, your frame with frame number WM20.22053 was despatched from the factory on 25/06/40, as part of the military contract C/6654. This was a contract for 4.000 bikes (frame numbers 21001 - 25000). The census number of your frame would have been C4197565.
Here’s a line up with brand new "sister bikes", this batch was used by the New Zealanders:
Your frame is not in the post war KeyCards, which means that it didn’t serve in the post war British Army. As it was found in Greece, it may have been used during the Greco - Italian war, when Britain was Greece's main ally. It provided Greece with a significant amount of military aid, including weapons, ammunition, and aircraft. The British also helped to train and equip the Greek army.
(The Greco-Italian War was a military conflict that took place between Greece and Italy from October 28, 1940, to April 23, 1941. The war began when Italy invaded Greece from Albania, hoping to take advantage of Greece's weakened state after the country had been defeated by Bulgaria in the Second Balkan War in 1913.
The Greek army was initially caught off guard by the Italian invasion, but they were able to mount a fierce resistance. The Greeks were aided by the difficult terrain of Epirus, which made it difficult for the Italians to maneuver their forces. The Greeks also benefited from the fact that the Italians were poorly equipped and poorly led.
After a few weeks of fighting, the Greeks were able to push the Italians back into Albania. The Italians were humiliated by their defeat, and they appealed to their Axis allies, Germany and Hungary, for help.
In April 1941, Germany invaded Greece from the north. The Greek army was unable to resist the German onslaught, and the country was quickly overrun. The Greek government was forced to surrender on April 23, 1941.)
The photo below (3 Nortons from contract V/7353 with Greek Army Police Officers) also seems to come from this period:
email (option): wd.register@gmail.com
Your engine with duplicated frame number WM20.113792 comes from military contract S/5209. This was a contract for 12.000 bikes (frame numbers 104818 - 116817). Unfortunately they are beyond the scope of the factory ledgers. But from the Receipt Cards we know that BSA started to deliver contract S/5209 in early September 1944, at 2.000 bikes per month. Which would mean that your engine would have left the factory in December 1944. Here’s a sister bike:
It is also not in the KeyCards, but again, it may have some Greek history as well. After WW2, Greece still had to conquer a civil war. See also here and here.
During the Civil War, the Greek Army (again) received British support. And this support formed the basis of the post war Hellenic Army. Your bike (or at least your engine) may have been used there. These frames / engines are often stamped with a Hellenic Crown with a number. You may find this on your engine as well:
email (option): wd.register@gmail.com