Electro Harmonix Bad Stone

The Bad Stone was released 1975 and produced until 1981. It was designed by Bob Bednarz, and was the first phase shifter to employ feedback in the circuitry. It compasses 6 stages of phases shifting with variable feedback. One specialty of this phaser is the manual mode, which lets you dial in the phase shift manually instead of using the LFO (low frequency oscillator). This enables a whole new dimension of sounds achievable, although no sweeping will occur in the manual mode.
[product info on DiscoFreq's Effects DB]

Featured in a video of Billy's huge collection of guitar pedals called Stompland.