The Meteor Distortion project is a clone of the Maxon/Ibanez Sonic Distortion, which first hit stores in around 1983. Advertised as a heavier Tube Screamer, in reality it shares nothing at all in common with the classic TS-9 circuit. It has more similarities to hard-clipping circuits such as the BOSS DS-1 or MXR Distortion+.
This project is for the original SD-9, but features one of the two mods from the SD-9M, the “Mids” switch. (The second SD-9M mod, the gain switch, is not backwards-compatible with this circuit.) The second switch on this PCB allows you to switch between different sets of clipping diodes.