Produced for only a few years, the IC (integrated circuit) muff is based on an entirely different circuit from any of the transistor muffs. It's not as scooped (fewer of the mid frequencies cut) and the sustain even more violin-like than transistor-based versions. Since being discontinued, this effect has acquired a cult following and appeared on several highly-regarded albums. The Fredric Effects ICBM accurately recreates the original, but with modern bypass switching and power filtering and an improved taper for the sustain control (so it's not all-or-nothing like the originals).
Thanks to Zaphod1989 for this early version of the ICBM 78 built in a Green Russian enclosure.