I found this star spectroscope in a steamer trunk that held a C-8 Classic in the back of my physics equipment storeroom 10 years ago, and have hung on to it ever since. (The C-8 has long since been sold.)
It has threads to screw onto the visual back of a SCT and three EP's for it; comes in a hand made wood box that is velvet and silk lined and marked "Star Spectroscope GOTO KOGAKU Japan".
I am assuming that one would use it to break light from a star or other object into its components. I have another picture of it out of its box as well, if you are interested.
Asking $50 which includes shipping and handling.