Union Switch & Signal Variations

*The following information in the description of the variations of M1911A1 pistols was obtained from "Colt .45 Service Pistols Models of 1911 and 1911A1", by Charles W. Clawson and in part from my own observations.

Serial Number View View

Description

No. 1041413 Left Right First day's production, the ninth U. S. & S. M1911A1 produced, without "P" proof marks and "Crossed Cannons" ordnance final inspection mark. U. S. & S. did not stamp the "Crossed Cannons" on any of their pistols. All U. S. & S. M1911A1 pistols were given final inspection by Lt. Colonel Robert C. Downie and stamped with "R.C.D." in a circle. Note the smooth Du-lite finish. All U. S. & S. pistols were finished using the Du-lite process and none were parkerized. The bullet ramp of the receiver was machined after it was blued leaving it bright unfinished with fine machining marks. Note the misshaped hammer spur and the poor alignment of the stampings on the right side.
No. 1062402 Left Right Has the "P" proof marks which can be found after about serial number 1060000. The "P’" on the slide and the receiver should always match since the same die was used to stamp the slide and receiver after proof firing. If they do not match then the slide and receiver are not original to one another. Has the Du-lite finish and all checkered small parts. No serrated small parts were used on U. S. & S. pistols. The "P" proof mark in this serial number range can be found stamped on the left side of the slide just above the slide serrations.
No. 1096273 Left Right Produced very near the end of the contract and has the "P" proof mark stamped just in font of the rear sight. The last pistol produced by U. S. & S. was serial number 1096404. U. S. & S. produced a total of 55,000 pistols in 1943.
EXP No. 94 Left Right Approximately 100 pistols made up from preproduction trial run slides, receivers, and small parts were used in various experiments at U. S. & S. Note the grind marks and metal missing on the right side of the receiver where experiments in stamping serial numbers or other markings may have been conducted. This pistol has the Du-lite blued finish over a sandblasted surface. This pistol was presented to Pete Benoit, senior manufacturing engineer at U.S. & S. during the pistol production.
EXP NO. 98 Left Right This example has a Du-lite blued finish over a polished surface, the other finish variation found in this series of pistols. Also has the characteristic grind marks on the right side of the receiver. This pistol was presented to Byron Light, an employee and member of the pistol integration committee representing U. S. & S.
Barrel Markings HS S P Normally found with High Standard " HS " marked barrels on the right lug. Also found with Springfield Armory " S P " marked barrels on the left lug during early production.
Grips Early Keyes Later Keyes Union Switch & Signal used plastic grips made by Keyes Fibre Co. Both styles have on the inside the strengthening ribs and the "K" inside the 5 pointed star. Early style without reinforcing rings around screw holes and later grips with reinforcing rings around screw holes. Date or serial number not known when the transition was from early to later style grips.
Magazines WWII Contractors Full blued tube with spot welded base and the top of the lip of the base marked: " L " M.S. Little Mfg. Co. , " R " Risdon Mfg. Co. , " S " Scovill Mfg. Co.. U.S. & S. pistols were issued with only these three types of magazines.