111 818 is definitely a Greek military identification number, here's a similar number on a BSA M20.
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And this is what Steve Madden wrote about these markings in 2009:
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Jan

email (option): wd.register@gmail.com

FYI, these are bikes from the same contract as yours. A lot of the C7183 bikes ("your" contract) seem to have been used in North Africa or in the Middle East.

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email (option): wd.register@gmail.com

Awesome! Lots of thanks for your answer. 😎👍
I had no idea that matchless goes around the world 😅
I have to learn many things 🙈

email (option): nicodapote@gmx.de

Here is a similar marking on my Matchless G3WO frame.

https://ibb.co/jTYZqhV
https://ibb.co/jGdR7CX
https://ibb.co/2gVGtgW

It has frame number 8336, which was part of contract C7183. One of 6,000 machines destined for the Middle East from 29/03/1941.

The other marking appears to be Greek, similar to those in this thread: 111 286 with the Hellenic Crown. This is only three digits different from 111 289 shown in the photo of the BSA M20 engine posted by Jan.

Does anyone know what these makings represent? Are they unique identification markings for individual machines, or machine type markings??

Any further information would be much appreciated.

Peter Wright

email (option): peter.h.wright@btinterner.com

My email address should read
Peter.h.wright@btinternet.com

email (option): peter.h.wright@btinternet.com