A comment from my side on the battery: I bought the MTL5B in 1988, and according to my information it doesn't require zinc-air battery (as mercury replacement). The MTL5B will be correctly powered with LR44 / SR44 or A76 battery.
This was the difference between MTL5 and MTL5B. It is therefore no problem to find common battery cells for the MTL5B.
My MTL5B served me well for more than ten years, when I changed to a Nikon F2. The MTL5B is a reliable mechanical SLR with a very unique and easy to use film loading system.
I think it's a very good camera to use with screwmount lenses!
Cheers, Sean.