Congratulations. The Pentax/Praktica/Edixa 42mm screw "universal" mount was used by many camera manufacturers in the 1960's and 70's. There are a tremendous number of Asahi Pentax, Zeiss,Yashica, Mamiya and even more aftermarket lenses available at very low cost these days. Most consider the screwmount camera a cumbersome antique. If you have an early Spotmatic with stop down through the lens metering you can use automatic, preset or even manual lenses and still have the benefit of the through the lens meter. If you have the later Spotmatic F or the ES probably you will want to buy newer Pentax lenses with the extra lever that can be metered at full aparture. Batteries of the correct voltage can be purchased from Freestyle and other mail order sources. The original mercury batteries are no longer available. Do not try to use alkaline or hearing aid batteries. If you have an accurate hand held meter, by all means check the Pentax meter for accuracy before you shoot some important subjects. Old meters often are not accurate through the whole range. Pentax cameras were precision made and last a long time. A real bargain used 35mm SLR. You might want to pick up a spare body on the web for $30-50. Even if the meter does not work you can still use the camera to make quality photographs.

I have a Spotmatic SP500, three Prakticas and a Vivitar 220SL all of which are 42mm screwmount and all sorts of lenses.