This is a Spectra Tri-Color, a color-correcting meter similar to my Gossen Sixticolor or the Collux 3, but with a special twist. Whereas most consumer colormeters measure and are meant to correct in two colors (red vs. blue), this one measures and corrects in three: red, blue and green. It's not like the others are bad--if you correct red and blue, green probably takes care of itself; it's the same thing in subtractive color--you set up a color pack for magenta and yellow, and cyan takes care of itself.

But the Spectra was designed and sold to professional cinematographers for whom matching exposures was critically important; the closer correction you got in the camera, the less work the lab had to to, which made for a better print.

This meter holds another distinction: it won an Oscar. Ever watch the Academy Awards show and they mention that was another ceremony for the scientific and technical awards, which wasn't broadcast? In 1976, this meter (or rather, William Blowers and Nasir Zaidi) won the Technical Achievement Award.

This is an update/reworking of the original Spectra Color meter from the late 1940s.