You are bidding on a manual (only) for a Moog MiniMoog Music Synthesizer, written in 1973 by R.J. Folkman.
Aside from its obvious usefulness for those of you who own MiniMoogs but who are missing the manual, the manual is full of schematic diagrams for oscillators, voltage-controlled amplifiers, filters, etc. that might be of interest to electronics hobbyists and musicians.