I recently purchased an old camera and attached to the case strap was a small leather case containing a small FFWB combi meter and instructions. A little research revealed that it is a combined Range Finder and exposure meter made in Germany in the 1950's. It fully works rangefinder wise, not sure about the exposure meter, although something appears to be happening, it's an extinction meter , in other words you point the front of the meter towards the scene you are wanting to photograph and peer through the back , larger opening and read off the dimmest lit number. You then line up the number on the top dial to coincide with the speed (in this case DIN number) of the film. Then you can read off on the opposite side of the dial an aperture and speed setting with which to take the image. Be interesting to test the accuracy..... It appears they were made in black and this rarer Grey colour. If anyone is interested in a full review of this little piece of history let me know..