Murray, here is something to consider...
...about 35 years ago, in a state not far from here, there was a young soldier stationed at a military base whose first assignment was as a cryptographic equipment repairman... naturally these machines were secret in nature when assembled and working, but almost without exception, the individual parts were available through normal channels in the supply system... so late one night while working the midnight shift in a very large repair shop, he gets the idea, that if he ordered one each of the parts of a particular machine that was bothersome to work on, he could create a test bench machine with which to troubleshoot defective parts, and he begins to order a half dozen parts at a time, throwing them in a box when they arrived... In the mean time, he constructs a jig out of wood on which to mount everthing and have his test bed environment ready for finally assembly... finally, after a few months, it was time to order the last remaining part, the frame of the equipment (that would normally be serially numbered on a plate attached with screws... and yes, even that plate was available through the supply channels in a blank state)... whle filling out the requisition forms, the repairshop was visited by none other than the crypto security officer who needed something fixed... recognizing the arrangement of equipment on the bench he inquired as to whose equipment was being working on, since he had not heard that there was a machine of this type broken... my (oops, I mean the soldier's) reply was that "nothing was broken, this was just a test bed being constructed to work on problem parts from other machines."
Well, you would have thought that the Russians had just nuked the capital of Idaho... He and the young solder had a long one direction conversation about how supply channels should not be used to collect parts to create an unaccountable secret machine! ... the young soldier then spent the rest of the night filling out forms to return each and every one of those parts... and of course the order for the base frame of the machine never got completed... BUT if that visit had never taken place, there would have been an unaccountable secret machine with no numbers in existence... shortly thereafter, procedures changed so that any major assemblies for secret machines had to be approved by at least 2 other people before the order was placed into the system...
Moral of the story? Never underestimate the ingenuity and craftiness of the resourceful soldier... An unmarked firearm in an arms room, made up of parts ordered one at a time and painstakingly fitted together by a bored and underworked unit armorer?
Not a common occurrence, but certainly not beyond the pale of possibility...
Congrats again Murray on such a fine piece as this Vickers... and keep this story to yourself... I wouldn't want the young soldier (now an old retired soldier) to hear about it and be embarrassed.
So when are you coming back to the Washington DC area?