The DGTM or Diabolical Gristle Tone Manipulator is a overdrive designed by guitarist Greg Koch (give him a listen if you haven't already) and T-Rex engineering of Denmark. The knobs are gristle(gain) tone and gravy(volume) and a toggle switch that goes between vintage crunch and a more compressed modern gain. Works very well with single coils.
Pedal is in excellent shape comes with box and manual.