1911 A1 Barrel Brisish Proofed Barrel

[twines]

I have a 1911 1A Type 6 barrel. It is Birmingham Proofed. I assumed it is a Lend Lease barrel. It has been suggested the proofs indicate the barrel was released for public sale and has no connection with Lend Lease. Can anyone explain the exact meaning of the proofs in connection with the Lend Lease program and how they connect with the civilian market. I know the literal meaning of the proofs.
Thanks

Tom