This is the
Boss MT-2 Metal Zone distortion pedal which , out of the box, has some decent sounds and tones but does need quite a bit of help in a few areas to get it up to speed and where it should be!
The tone section has been reworked to get rid of the nasty icepick highs and the well known nasal mids, better bass response as well as more precise tonal adjustments have been introduced into the circuit, highly tweakable tone controls!
Slightly more gain has also been added as well as the clipping section being altered giving the overall distortion a much smoother sound ...no more unnatural buzzsaw grind , much , much better and more pleasing to the ear!
Many electrolytic and other inferior capacitors / resistors have been replaced with high quality metal film components of the same and different values which yield superior clarity and tone!