That meter is the old standby Weston Master II. This meter uses a selenium cell and has 2 ranges. The door on the back pops up open for low light and is very closed in bright light. All in the entire meter works very well. The readings it output are consistent with the meter on a Nikon FE2. Best of all, this meter is very cheap.
Using the meter is very easy and simple. To start, users have to set the emulsion speed. Press the button located at the bottom of the meter and then pushes the little tab that sticks out from underneath the main switch dial until the speed setting users want is visible in the little window. If a user can’t see the window, turn the main dial until they can see it.
To get a light reading result, hold the meter in front parallel to the ground and read the number the needle points to. Rotate the main switch dial until the arrow on the dial points at the number and then read the aperture and shutter settings from the dial. That’s it. As with any light meter, always remember that the reflectivity of the surface you are reading will surely affect the readings. On any meter, light colored ground surfaces will tend to give a setting that produces underexposure.
There is also Weston IV Light Meter. The IV’s were made and produced in the UK and imported into the US. This is the last units of the Masters to feature the white-on-black meter face. After that they would be black on strong bare metal.