Maker: Photo Research / Spectra
Model: Color meter (aka Three-Color meter)
Cell type: Silicon
Measure type: 2D Incident
Original Battery: two TR-113R (4.05v each)
Modern Battery: two PX25 (4.5v each) and some way to compensate
I know that this meter came out at the end of 1948 because Google scanned back issues of Popular Photography magazine, and this appears as a blurb in the November, 1948 edition, p. 151. So you can say all you want about them but I for one welcome our new overlords; and the more I think of it, the more I figure that if Google did run the country, they wouldn't do as poorly as the people who've been in charge for the past few decades, regardless of party.
My copy of this meter came with the original hard case, a box with the original batteries, abut no instructions. This is where Google pays off again because Popular printed a small blurb about how to use it, which I quote here:
If it's like anything else Photo Research (PR) made, they made it for a hell of a long time before updating it. This one was replaced by the Tri-Color meter of the 1970s.
Click on any of the photos for larger versions. Left is the "back" of the unit, with the meter face, the switch, and the battery chambers (top). The middle image shows the front of the unit (note the trigger) and the Lumi-Sphere in place. The right image shows the unit with the Lumi-Sphere removed so you can see the filter masks.