This is a model M-S-B. If you read my write-up on the Model M-S, you'll notice how much different this looks from the M-S. It's a completely re-designed unit. It doesn't need batteries and it's in a much smaller, bakelite case.

Movie Makers magazine (December 1935, p. 526) describes it this way: "A new model of the Rhamstine Electrophot, a batteryless meter, has just appeared. This is known as the MSB and, in general appearance, compactness and finish, it resembles the MSA, its predecessor. However, the improvement in the new model lies in the fact that its scale has been extended and readjusted so that readings under difficult lighting conditions are indicated very clearly, with better separation between the scale indices. The scale now has a very readable silver finish, with numerals in black, and it is arranged to give direct exposure readings for still and movie film of the kinds commonly used. Other conditions can be covered by reference to a chart attached to the meter."

Just as a note about Rhamstine meters: one of the things that makes it extra hard to research these is that there are no patent numbers. Every Rhamstine I've seen is "patent pending," from the earliest I own (the M-S) to the last (a 14-A). They may have actually filed patent applications but I can't find them. Yet Weston, General Electric, and other contemporaries all managed it. Make of that what you will.