Maker: Bell & Howell
Designed by: Albert S. Howell
Design Patent #: D 81,981
Measure type: Comparometer
Battery type: one C cell
Bell & Howell made movie cameras. Their earliest line was the 16mm Filmo from the mid 1920s. They had a great advertising campaign in old National Geographic magazines where they showed people using Filmos all over the world. So they were tied to adventure and travel and exotic locales.
This was an important accessory. I haven't seen advertisements for it yet so it's been tough to research. I'll update this as I learn more about it. The age is from 1930 (the date of the design). One of the bands is calibrated to use with Filmo models 70 and 75, which were their late 1920s offerings. The patent ID refers to a date (1924), not an actual patent number, so I haven't yet found what the patent refers to. There is an article about it in an old magazine from 1931; but I haven't purchased it yet and haven't seen it; and it's too obscure for the local libraries to have.
In the meantime: this is a smaller, earlier version of the SEI Photometer, but the principles are the same. The're a lamp inside, so what you do is look through the eyepiece (the bell end at the top) at whatever you want to measure, hold the button on the side, and twist the bottom of the handle to vary the intensity of the bulb inside. When the light from the bulb balances with whatever you're looking at, you can calculate the exposure.
Exactly how the calculation is done--I haven't figured out yet. The top band has the frame rate and the middle band has the aperture scale. The bottom has graduation marks but I haven't quite figured how it all matches up. That and the bulb is burned out and needs to be replaced, so I haven't been able to test it.