This is a Colt branded KCB-77 bayonet manufactured by Eickhorn Solingen in West Germany.
This bayonet that I have was claimed by the previous owner to be a prototype from the U.S. M9 bayonet competition, but I DO NOT believe this to be the case. I say this because I cannot find any reference to Colt being involved or partnered with Eickhorn Solingen in anyway during the M9 bayonet competition.
Having said that, I can only find a couple of references to this bayonet. One reference shows photos of a commercial version, sold by Eickhorn Solingen, with a green scabbard and green handle. My example has a black scabbard and black handle. “The Book Of Colt Memorabilia” shows this bayonet on page 118 of Chapter 7 Colt Knifes. It is referenced as product CT39A.
I can only speculate that Colt made some deal with Eickhorn Solingen to produce some of these for the retail market (keep in mind ES had made some M7’s for Colt previously).
The bayonet has a built-in wire cutter (with electricity sensing/light emitting diode), bottle opener and straight-edge screwdriver. The LED is built into the handle and is supposed to light up when the wire cutter comes in contact with an electrically charged fence thus warning the user.