Hans Buchholdt , Oct 01, 1998; 05:06 p.m.
Arthur...wow, an old pentax question...I think it goes like this.
Pentax got famous with the Spotmatic series that had the universal (aka Pentax, M42) screw mount. A nice system, but when you took off a screw mount lens, you'd never really know exactly when it would detach from the camera body - a bad thing, however wonderful the Spotmatic bodies are.
To fix that problem Pentax introduced the K mount. The initial bodies were the K2, KX, KM (all of which had motordrive versions), All of which were not dissimilar in design to the last models of the Spotmatic series. The K2 was the top of the line Pro body, the KM was the economy model, and the KX was something in between. Later when camera bodies got smaller (the Olympus OM-1 changed everything) Pentax introduced the ME and the MX - for a while they maintained the K2(DMD), and they dropped the KX. The KM, with some minor improvements became the K1000, the modestly priced, modestly featured camera in the Pentax line.
There wasn't anything wrong with the KX behond size and weight. It was replaced by the smaller/lighter MX. I'd figure KX body is something of a rare find these days, they were only made for about 3 years in a time when camera designs didn't change that much.