A friend of mine bought a MESA Grid Slammer, a very nice sounding overdrive. Out of curiosity I borrowed it from him and decided to do my best at tracing the circuit. Here's a few pictures from the tracing process.
This resultet in the schematic below which turned out to be nothing more then a TS-9 with a different diode clipping setup (as seen in Paul Cochrane's Timmy overdrive). Here is a vero layout I made for it that sound exactly like the original.