This is a slightly less elaborate varation of my Bertram Chronos. They still fashion it after a large pocket watch, complete with a small chain and fob (mine's missing. I'll have to put something on it). This one doesn't have the spring-loaded top, and the front "eye" portion is simply glass; there are no swing-out doors to protect it. Otherwise it's pretty much the same thing.

Mine is a later model, as the calculator dial is calibrated for DIN, Scheiner, Weston and ASA. What you do is set the exposure index on the upper calculator dial and that tells you a letter code to use. You set the letter code into the little calculator dial on the bottom and then turn the big dial to match the Light Value on the meter scale. That gives you an aperture/speed pair.

The scales look confusing at first but it's easy after you look at it a moment. The scales are calibrated in full half stops, which is nice because that's the way most camera shutters and lenses are stepped. Weston uses 1/3rd stop increments, which works great for film speeds but not so great on camera lenses and shutters.

These sold in different colors; I've got two, one in black and this one, which is kind of an off-white.