This is an MXR overdrive pedal made from 1981 to 1984. It's an overdrive with a dry character and a gritty, well-defined sound. When you turn up the distortion knob, it distorts deeply. It gives the impression of a rough distortion, much like the Distortion+. It has a cheap, plastic enclosure, but it produces a good sound that's characteristic of old MXR pedals. The footswitch is very difficult to step on, and it sometimes doesn't switch properly unless you press it straight down. Looking at reviews online, many people mention that the switch is unstable and doesn't switch unless pressed from directly above, so it's probably just the way it is. Indeed, it switches without any problems when pressed firmly and straight down by hand, so I think it's a structural issue. Due to the cheap enclosure and the aforementioned unreliable switch, it's recommended to integrate it into a board and switch it with a switcher for live performances.