I bought this Rockman (Tom Sholz) Guitar Ace from Sam Ash music in Orlando in September of 2001.It is in excellent condition. I am selling the Guitar Ace and instruction manual only. No headphones.

Dunlop made several versions of this device, for bass and guitar.  This is a portable practice amplifier, with effects built in, that you clip onto your belt and use with headphones (not included) for practicing. There is a guitar input jack as well as an auxiliary input for injecting audio from a music source (to play along with).   In general you will use headphones, but you can connect a cable from the headphone output jack to the input of an amplifier.  The effects built into this device are built around the Tom Sholz sound in terms of distortion, sustain, and compression, and some people use this as a primary effect to get that Boston sound  while playing through a PA or clean guitar amp.  The control options are simple. There is a single volume knob and two switches used to control the amount of effect and distortion.  

The Guitar Ace runs on a 9V battery that switches on when you plug in the guitar cable.  You can power it with a 12V AC adaptor (not included), but then you give up portability.