BOSS BF-2 Flanger effect pedal. Serial No. 0400, made in Japan around March 1981. By modulating a slightly delayed audio signal, it produces a so-called jet machine effect. It works on a similar principle to a chorus effect. A classic model with a purple body and four black control knobs. I used it on my effects board until around the mid-1980s, but haven't used it since. I confirmed the effect during a power-on check. - Model Name: BF-2 - Type: Flanger - Brand: BOSS - Color: Purple - Number of Control Knobs: 4 - Input Terminals: 1 - Output Terminals: 1 Thank you for looking.