Picked this up at a thrift shop because I could tell it was some kind of color temperature meter, but didn't know what. Even though it's not marked, it turned out to be made by Gossen in 1952; they would later make the handheld Sixticolor and the others. As far as I know, this is the earliest.

Using it is pretty simple. There's a little leg on the back of the main unit so it'll stand up, or you can hold it in one hand and the wand in the other. You aim the plain gray face of the wand at your light source and read the dial on the rear. There's a thumbwheel adjustment on the bottom, so you can turn the wheel until the meter needle nulls in the center, and that tells your color temperature; you can then look up the necessary filters you need to correct the light. Or you can set the scale on the wand to the color temperature you want, and place filters over the sensor until the meter nulls.

You can't get a sense of scale here, but the meter is about the size of a pack of cigarettes and the wand like a typical magnifying glass. Very light and easy to handle. It's much smaller than my Collux 3 or my Spectra Three-Color.

I don't have the instructions but it's pretty simple to figure out, except for one thing. On the side of the meter housing there's a flap held by a screw: if you loosen the screw you expose an opening that's for——I don't know what. If it's for a battery, I don't see the contacts to make current flow. Maybe it was for an accessory that's now gone. I hope to find out someday.

Ed van der Aa has a great page for this meter at his own website. Click on the info link on his page for more.