The inspection system must have involved a lot of resources if the Air Ministry had their own inspectors with a manufacturer of side-valve motorcycles ! The Norton 16H hadn't been "cutting edge" since the early 1920s
I would be fascinated to discover more about the RAF contracts. "Air Publication" workshop manuals turn up quite often but I have never seen Air Ministry parts lists (which generally showed frame and engine numbers) and any surviving machines now seem impossible to identify. Perhaps I should be looking for A.I.D. stamps.
I fear that the various and changing relationships between The War Office, Air Ministry, Ministry of Supply etc. are likely to remain something of a mystery to me.
I had wondered as well about the "JLO" on the crankcases. I know them only as a post-war proprietary engine manufacturer. My Norton was engineless when I obtained it and I know nothing about the history of those cases which I bought at the Netley Marsh jumble last year. I was looking for an engine from contract C.5109 (W1000 - W6999) to pair with my frame no. W4216 and was quite chuffed to find W4187, Once fitted to a bike only 29 earlier.
The engine and frame probably left the factory on the same day in 1940 and are now back together after 66 years ! It would be even more of a co-incidence if the engine had been left behind in June 1940 as well.