This is an example of an Engineering Concept Model rarely seen outside of the Colt factory. These are used in the first stage of testing to see if it is desirable and patentable. This particular piece originally came from the estate of a former Colt Engineer whose work and patents involved the Colt Colteer .22 rifle, .400 Colt Magnum cartridge, Model 1971 stainless steel pistol and rifling the M16. This model is constructed of solid aluminum with a steel bolt assembly and is exploring the concept of a lightweight semi-automatic pistol with a longitudinal magazine located over and in line with the barrel. The dynamics of moving a cartridge backwards and down into the chamber were being evaluated. The second concept would appear to be the one-piece frame and barrel without the traditional grip magazine. Being in the first stage of testing, the pistol has no markings. This model never progressed beyond the first stage. The pistol is accompanied by letters describing the model and some brief information on the Engineer, who was not named.

Very fine with some minor scratches, probably incurred during manufacture and testing. A very unique and rarely seen out of the factory Engineering Concept Model.