I am not an expert, but will tell what I know until one shows up.
The "779" slide is known as the military match hard slide. They were made for the US Army by Colt, Drake, and I have seen them marked TZZ for IMI - Israel. I do not think they are in production now, all you see are military surplus, and they were not sold new commercially.
There is no corresponding receiver. A military match pistol would have been made by putting a new barrel and slide on an existing frame, and otherwise accurizing the assembly.
Some gunsmiths will tell you they are not as good as current production commercial slides from makers like Caspian. I am not qualified to judge, but my local gunsmith has assembled some very accurate pistols under "779" slides. He does prefer Kart barrels to the "779" type.