That is the original Kadee N coupler from the late 1960s. Originally called an MT-5 (or MT-3 preassembled), it was renumbered 1025 after a few years. They're still my favorite couplers, mostly because they pretty well match the thickness of the center sill on most cars, instead of having a huge lump like the 1015 case. Many people don't like them because of the way the spring can react when pulled.
It was an offshoot of their HOn3 coupler, which, as far as I know, was the first split-shank coupler made. Some HOn3 modelers use the N couplers, and they work quite well with the HOn3 versions.
The coupler itself is identical to the one in MT's truck-mounted couplers. If you have a lot of those, and want to body mount them, MT will sell just the draft gear cases, in brown or black. I bought 500 pair several years ago.