Those Zeiss models were finely crafted build like tanks. The selenium cell meters will probably have died by now. Also the Kodak Retina models (SLR and rangefinders) used wonderful Schneider lenses.
After an accident in the Alps, where I dropped my Leicaflex with three lenses off a cliff, I used my Retina Reflex III for a while and the Kodachrome slides I took easily compared with those from my Leicas. Before the Kodak plant in Stuttgart, Germany closed, they offered to overhaul (almost) all cameras for a minimal amount (26 DM, if I recall) and I got my three Retina Reflexes cared for a nominal price. (Kodak’s demise is a shame.)
Sadly, the Contaflexes and Retinas haven’t held their value and don’t command the high ebay prices that almost anything from Leica does. Jeremy, if your Contaflex is in such good condition, I’d keep it for memory’s sake. And who knows how the photo market will evolve?