I was recently given a Weston Cine Exposure Meter (Model 819) by a relative. It doesn't seem to be reading light properly and I'm wondering if there is a battery that needs to be replaced? I've tried to take it apart but cant figure out how to. Does anyone have any suggestions for how to open these meters and if they actually take batteries? I'm primarily a film photographer and I realize this meter was made for motion picture film. I've attached two photos below for reference. Just curious if I could use it in my workflow, any help is much appreciated. Thanks.