There were a few variations of both cameras and lenses. None bring high prices but can still be very usable cameras delivering high quality results. Most required stop down metering (a black slide switch to the right of the lens mount as you face the camera). The Spotmatic F did not.

The Takumar lenses were/are very good. A 50mm 1.4 lens will be more desirable than the 1.8 or 2.0. Series (over time) went from Takumar to Super-Takumar to Super Multi Coated (SMC) Takumar.

As Ian suggests, could be corrosion holding the battery cover. Or just age. Try various coins to get the closest fit. I would prefer a drop of liquid penetrant as opposed to WD-40 in the spray form. Best to do this first to avoid marring up the bottom.