I think it's fair to say that what the Nikon F was to the pro market, the Spotmatic was to the amateur SLR world. TTL metering, solid build quality and for the time a very modern spec made for a compelling option, and use of Contax/Praktica's M42 screw thread made sure that there was access to a vast range of lenses - the excellent Takumars from Pentax, of course, but countless others. In fact it did so well that many people came to think of M42 as "Pentax Screw", which it wasn't really... There were many versions of Spotmatic over the years, with mostly very minor variations - I'm going to skip the earlier models and concentrate on 1973's Spotmatic F, the last and greatest model, that featured full aperture meeting with SMC Takumars, which featured electrical contracts for passing aperture info. Other M42 lenses can be used with stop-down metering, and there's a stop-down switch on the side of the mirror box to activate it. Otherwise, it's much like most Spotties, and nothing wrong with that - a very standard spec, shutter speeds 1s to 1/1000, all controls where you would expect them, a decent match needle arrangement in the finder, and a nice screen with a microprism spot. What's good about it is the way it feels and works - properly made, smooth even now, capable of results as good as the glass you put on it. Then as now, or perhaps rather now as then, the Spotmatic is the standard by which all similar cameras are judged. It's a lovely bit of kit.