The British Purchasing Commission was established in the U.S. in 1939 for the purpose of buying war material for England. After the huge loss at Dunkirk, fearing an invasion they bought small arms for the Home Guard from several U.S. gun manufacturers, including just about every handgun Colt had on their shelves. It didn't matter what type or what caliber. The first shipment from Colt first went to Winchester where they were packed with the correct ammunition and then forwarded to England.
These weapons had British inspection marks, but were not military proofed, and some had the British "Broad Arrow" property mark, which the Model 97 in question does not have. Again, it was 20 years too early for British Purchasing Commission purchase. The commercial proofs on the Model 97 Winchester were used through 1954.