As mentioned earlier there are many options for M42, I have 6 or 7 M42 bodies some of which are holding up better than others. I still have my first Spotmatic bought in the 1960, the meter is not accurate but the shutter is dead on. I have another Spot with a good working meter, I bought a battery converter before I learned that for Spots a converter is not needed. Spots use stop down metering are rugged and very basic. The later F and ES (sutomatic shutter speed) bodiesuse open apature metering and some Fs and ES could be fitted with a motor drive. I also have a Chinon with a winder, good solid camera but the winder is only just working. Chinon, Ricoh, and Cosina made cameras for Sears, Ward, Penny's and Vivitar, again very basic but rugged cameras and cheap on Ebay. I have a Mamiya that used the M42 thread but a different pin system so my Pentex M42 lens dont meter at all, not even in stop down. Mamiya also made stop down metered single pin boides with a spot meter, the 500 and 1000. Yashica and Fuji made variants of the M42 mount so you need to be careful about the model so can match the standard M42 lens with the correct body. On the high end Alpha and Context made M42 mount cameras as well. Most of the older cameras used 625 mercury batteries, you can find converters, use Winn Air or hearing aid batteris.