Actually any firearm sold commercially in Englandhad to go through either the Birmingham or London proof house. A brand new firearm imported from the U.S. that was to be sold commercially in England had to be proofed. As long as the firearms sent to England through the Lend-Lease program remained in government hands, they did not have to be proofed, but once released for sale they had to be proofed regardless of whether they were to remain in the country or be exported.