images via this auction"This is the first of three of Leon Russell's Sequential Circuits Pro-FX Model 500 racks we'll be selling. These are rare. This one is loaded with five parametric EQ modules... Here's some useful information I found online... From what I know, there were only 200-300 systems of various configurations produced by Sequential Circuits from summer 1982 to 1983. Eight modules were produced in the systems two year life span including 510 Distortion, 512 Phaser, 514 4 x 2 Mixer, 516 Parametric EQ,518 Reverb, 520 Transpose / Sync, 522 Flanger / Chorus and 524 Digital Delay Line. Sometime in 1983 the Pro-FX was re-marketed as the "Pro-FX Ambient Package" which consisted of the 500 System Controller as well as the 518 Reverb, 522 Flanger / Chorus and 524 Digital Delay Line."
