This is a vintage 1970’s Dan Armstrong Red Ranger electric guitar effects pedal. This original issue sound modifier/booster unit is considered a classic effect which enhances treble, bass or both concurrently. Made by Musitronics Corp. (Mu-Tron) the company perhaps best known for their colorful envelope filter (the Mu-Tron III), amazing octave divider and great phaser units. The Dan Armstrong “Sound Modifier” small effects unit line, which were denoted by color, includes; the Orange Squeezer, Green Ringer, Purple Peaker, Red Ranger, the Blue Clipper, etc., all of which were designed to plug directly into the guitar or amp. Constructed from extruded aluminum square tubing riveted with painted cover plate, this extremely simple distortion effects unit has a male hard-wired 1/4″ output jack and a single mini-toggle control.