The Version 3 Big muffs (1976-79) were the first muffs to have an AC power in and some featured a tone bypass switch. Looks wise the now familiar red and black paint job featuring the Pi symbol was used. The very first V3's however had none of this, no Ac Jack, no tone bypass and in fact the circuit was exactly the same as the V2 Big Muff ... And THAT is what you're experiencing with this pedal.
Featuring the BC-239 transistors and the exact circuit in a V2 Ram's head edition this rare muff certainly is a nice piece of Pi.