I'm not very keen on Ron's abbreviation. R. Sigs or Royal Signals are acceptable..but they were a 'Royal Corps' from the time they were founded in 1920 :-)

AA Command are indeed a devil to research and don't appear in the early-war Home Forces listings. As Rob suggests, the interaction between RAF and Army may have meant that they were outside of the norm.

I'm not sure that they'd have needed an arm of service serial, as they weren't working within any Corps, Divisional or Brigade structure. Their formation sign and a blue / white sign was enough...I can find no reference to any use of a a panel other than square in Army documents....somewhere there must be the 'Rosetta Stone' of Ack-Ack markings.

A lovely image Ron. The G3L is a very early example - note the lack of pannier frames and the tabs to attach such on the rear carrier. Also note the ribbed front mudguard, lack of a front-stand and that the rear frame is the early type with the "sandwiched" plates inserted into the frame tubes where the rear wheel spindle attaches, rather than the cast lugs..........

Have a wade through this then Rik. 'The Wire' for the whole of 1940. Ron

https://www.royalsignalsmuseum.co.uk/wp-content/wire/Wire1940.pdf

email (option): ronpier@talk21.com

I even found a picture of a Chief with a census number near to the Chief I restored this year for Tim. So this one is also one of the 300+ ex French CAV's that were reallocated to UK after the fall of Paris. Ron

email (option): ronpier@talk21.com