Just a variation of the Big Muff from a small danish company, all the modifications are well known. But it's a very good mix!
The schematic is included in the manual:
I haven't built it and you might notice I'm not sure what some of the controls do! I may have got some of the pots the wrong way around but that's an easy fix if you build this. I think it's right - if you have any issues let us know.