MXR MX-120 Envelope Filter USA in excellent condition and in full working order.

These MXR MX-120 Envelope Filters were made in 2 versions. The First Serie Version 1975-1976 were without LED and without Power supply input. The Second series were produced in 1981 till 1984 but included a LED and a Power supply input.

Quoted from Crave Guitars :
During the late 1970s and early 1980s, New York-based pedal maker MXR Innovations was turning out some very credible effect pedals such as the iconic Phase 90 and the classic Dyna Comp. A lesser-known model in the MXR range was the Envelope Filter, which uses the dynamics of the input signal to trigger an analogue filter sweep, resulting in an auto wah-type effect, much favoured by funk, soul and disco artists at the time. The early first generation MXR pedals featured a ‘script’ logo and model name until about 1975/6, when they changed the design to the more common, modern ‘block’ font. What is it with auto-wahs and the colour beige? It seemed to be the de facto colour for some envelope filters at the time, including the BOSS TW-1.