Recently traced by Aion Electronics. Schematic is avaiable HERE.
Mode and XLF switches was internal DIP switches in original units but is moved to the outside per Aion Anomaly Vintage Distortion project. Schematic and circuit info is avaiable HERE.
Designed by Dan Coggins (Lovetone and Dinosaural). Despite its name it is more like an overdrive with asymmetric soft clipping and a tone control that pans between a low pass filter and a voltage divider.
*Update 221110*
Corrected two resisor values and Zener diode values according to the a new schematic.
Pretty cool design; a Rat and a Tubescreamer in one box with a "Contour" control that looks like the Mid control in Wampler Triple Wreck...
A fairly rare old Boss eq pedal which is rarely cloned due to the dual 10kA/10kC Balance control. However, it is quite easy to make your own if you have a dual 10kA pot and a single 10kA pot on hand. Custom pot tuturial and schematic is avaiable HERE.
Slightly modified, subbing the two single op amps of the original to a dual. 1458 or 4558 should match the spec of the original ones.