British Proofed Colt 1911A1 question

A friend has a Colt 1911A1 that has all the expected Birmingham Proofs as required under the Proof Laws of 1925. One that I can't I.D is stamped on the frame in the area between upper grip and trigger guard. It consists of crossed swords and from left to right, at 9 O'clock, the letter "D", at 6 o'clock the number "5" and at three o'clock, the letter "B".
Can anyone tell me what this stamp represents ?? Thanks, Joe

The D on the left side and B on the right side indicate that the pistol was proofed in 1953. The number 5 at the bottom is the number assigned to the inspector that did the proofing.