I am pretty far along with an article on the Aluminum case loads I was going to send the Journal also. I have seen and documented orange RG loads dated 52 and 55. I have MOD documentation that trials continued into 1949 and that Woolwich did testing on the BSA machine carbine with ammo that was three years old before DG of A directed the acquisition of 20,000 cases (orders were split between ICI and RG) It looks like DG of A finally directed the cancelled the 9mm project in what must have been 1953 or 1954, but subsequently the OB conducted a trial using both the RG and ICI cases and I think this must be where the 1955 & 1956 case came from. I have never seen a document cancelling this project except for an undated (in the part I have) after action report on British Aluminum case ammunition. There is reference in the material I have to RG having two annealing process, the “1949 treatment” and the “1952 treatment” which is how I can guess at the date of the order for 20,000 cases. In truth there is no evidence that 20,000 cases were delivered. The “1949 treatment” RG cases were used in the BSA machine carbine test, or so the documentation implies.
I have the early trial reports, but that file ends in 1948. I have some guesses on where some of the rounds pictured in this thread fit into the story.
PS: Good eyes and memory for a man your age!!! It is indeed the drill round you were kind enought to pass along. I have cleaned it up a bit and my drool marks I left when you first showed it to me are now almost invisible.