Pál_K
Cameras. I has it.
…I would put money down on an early 60s Spotmatic being more likely to have all of it's shutter speeds working well than an early 60's Contax having any shutter speeds working at all, if neither of them have had any servicing since they left their manufacturers.
(This turned out to be very long-winded; maybe just read the first and last paragraphs)
Whether the Contax shutter would be functional may rely on design tolerances and expected periodic maintenance throughout its lifetime. Mechanisms with high precision and close tolerances are more likely to have failures than another mechanism with looser tolerances.
For example, long ago on a favorite mechanical watch website, TimeZone, a highly respected and experienced watchmaker stated that the small dirt particle found in a friend’s still-working 30 year old Rolex would’ve stopped a Patek Philippe in its tracks. Think of the Rolex movement more like a Chevy 350 and the Patek Philippe as the diabolical Porsche 550 quad-cam. For a less tony example, consider that a military rifle will have tolerances and a chamber to accept ammunition from a wide range of suppliers of varying quality and is designed to not fail in harsh environments with dirt, sand, snow - whereas a high-precision benchrest target rifle of the same caliber will have a tight chamber and throat and may not even be able to chamber the military version of the round (e.g. 7.62x51 vs .308).
I don’t intend to imply the Spotmatic is a crude battle-axe (I’ve worked on them and they’re wonderfully designed). Rather, I think the Contax suffers from its own brilliance. DAG said the Leica M5 was overengineered; I think the same may be true with the Contax.
But perhaps design for longevity and resistance to the elements is perhaps the better design.