This Colt M1911A1 was produced some time in July or August of 1945. It was part of contract W-19-059-ORD-1751 / W-19-059-ORD-2182.
This is a late production M1911A1 that utilized Colt's Parko-Lubrite finish. Colt adopted this finishing process in early 1945. It's very close to parkerizing but has a finer grain structure and is smoother to the touch.
This particular pistol was inspected by J.S.B. or John S. Begley. John Begley was a Civilian at the Springfield Ordnance District. He was the Army Inspector of Ordnance from July 15th, 1945 until December 5th, 1945. Due to the short period of time and timing with the end of WWII, not very many pistols with his mark have been observed.