Thanks!
You might have seen this before:
http://www.rangefinderforum.com/forums/showthread.php?t=65691
It is about right what I said.
Does it have a screw underneath it with a zero? That would be to reset the needle to zero position in the dark or close to it. Just block the cell and see if the needle stays at zero. It is similar to the zero reset on a Weston Master light meter.
It uses a PPX625 battery. Your best alternative and cheaper is to use ZA675 hearing aid batteries with a O ring as a spacer.
BTW, it seems to be functionally similar to the Asahi Pentax meter for the S series screw mount cameras.
Enjoy the Kopil!