You dont need a battery for this cam to work. This means you can use it manually, too. To start with it, I would recommend hearing aid batteries. If you like the cam you can either look on ebay for mercury cells, or buy a cheap schottky diode and attach it.

When you watch through the viewfinder you see the frame. The rangefinder has paralaxe correction. Which means when you change focus, the frames change, too. If you take a pic at minimum distance nearly all you see in the frame is on the negative. But if you take a picture which is 10 meteres away, you see only ~80% of the pic in the frame. Same as with all other rangefinders.

Now set the cam at minimum distance, 1-2 meters and test it. Put an object at top left of the frame and take a picture, put the object top right, bottom left&right and take pictures. Then check the negatives. Then you will see if and in which direction (left or right) the viewfinder/frames needs to be adjusted. You see where the frames are and what information really gets on your negative.

Which means: under the top are some screws with which you can move some things/mirror and with which in the end the frames you see in the viewfinder move ;)

I just purchased a G-III off ebay recently and I am new to shooting with a rangefinder. I was wondering if you could tell me what you meant by “adjust the viewfinder” I am still getting used to how this camera works! I don’t currently have a working battery in the camera and I was wondering if that was affecting what I see through the viewfinder.

Thanks so much, I hope my question isn’t totally amateur!

About batteries: Once I bought 10 original px batteries in one pack cheap on ebay. They last forever ;) If I wouldnt have them, I would insert this diode between the wires. It costs just nothing. Hearing aid and winecells are too expensive for what you get, in my view. See the pdf I linked above.