I have sold the KM23 engine parts to Nick as he already has some of the parts to build a complete bike. I had those parts as well before the fire but none of these parts survived and I currently don't have any space to restore motorcycles. The War Office KM24 engine was also completely melted due to the fire.
@Klaus: The paint on the rockerbox was applied by the Army as these War office KM23's were stocked at the BSA factory in civilian trim. In September 1939 after the declaration of war an immidate delivery of available motorcycles was arranged from various British motorcycle manufacturers. BSA delivered civilian KM20's, KM24's and KM23's in the 1st 3 weeks of September. Some of the KM23's and KM24's were delivered within KM20 frames.
Engine KM23 141 was delivered on 26-09-1938, to Boyes or Byes in Bromley. I don't have the BSA records for 1938, so I can not check the other engine number.
@ Ian: I don't have any more parts from the bike yet but the seller of the engine told me that the owner in France has a very large heap of original frames and the engine once came to him within a frame. I am going to try to have the owner look for the frame in that heap of frames. France is the best place to look for these rare early parts, many of them still survive there but it's often difficult to convince the owners to sell the parts/motorcycles.
With regard to the factory record for engine KM23 141, it looks to me as if the dealer was "Boyer" Bromley. Later run by Stan Shenton and linked to the Boyer-Bransden ignition system.
Engine No. JM23 837 was one of a number despatched in March 1938 to BSA Copenhagen. The sheer number being sent to a small country like Denmark during 1938/1939 makes me wonder if it was a back-door to the German market in the face of trade restrictions.