In the words of JHS Pedals:

In 1967 the legendary Mike Matthews started experimenting with
circuits for the electric guitar, and by early 1969 he had created a
circuit that has become one of the most legendary, collected and
mythical pedals in the history of guitar effects. With 30+ versions made
throughout its almost half a century lifetime, the Big Muff
Distortion/Fuzz has personally pioneered the sounds of some of the
biggest bands and musical movements in history. The Muffuletta is our
tribute to the legend and story of one of the greatest pedals ever
invented.