In the early 1970s, Colt wanted to develop a new military pistol so that it could offer a modern replacement for the venerable 1911. Colt Engineer Robert Roy designed the new gun in 1971, and was granted patents on it in 1972. It was made entirely of stainless steel, had a 15 round capacity (in 9mm; 12 rounds of .45 ACP in that version), and a DA/SA trigger along with a manual safety mounted on the slide. In fact, the gun shares many elements with Charles Petter’s pistols, the French 1935A and the SIG 44/16 family (which became the SIG P210). It has full length frame rails, and a modular removable fire control mechanism, along with a barrel ramp to lock and unlock in place of Browning’s swinging link.
The Colt 1971 prototypes became the Colt SSP (Stainless Steel Pistol), and were entered in the US military XM9 trials in the 1980s, where it ultimately lost to the Beretta 92. The SSP (and the 1971, for that matter) was never offered on the commercial market, although it certainly would have had potential there in the 1970s.