Well, I use a 30 year old Mamiya DSX1000B, it has spot and average metering and uses M42 lenses (but some models need that you stop down for the meter to work). It works even without batteries (but no meter) and has speeds from 1/1000 to 1 second and a bulb mode. Also, remember that they're FULLY manual, so forget about autofocus or aperture priority.

They're really cheap in eBay, 20 euros the body only. And are solid as a rock.