This accessory was listed in a 1980 price list; not one earlier (1977) nor later (1985) as far as I can tell. Photos courtesy of Steve Brennan. According to Steve, “it is suited only for bright stars but a curio nonetheless. You will notice from the pictures that it is attached to the 1″ eyepiece via three screws, crude but effective”.
Note: Spectroscopy can be used to derive properties of stars, such as their chemical composition, temperature, density, mass, distance, luminosity, and relative motion using Doppler Shift measurements. See: https://en.wikipedia.org/wiki/Astronomical_spectroscopy for additional information on the subject.