I have listed four Polyfusion modules made in 1975 that are the only ones that I have found to be made in a Moog modular (synthesizers.com compatible) format. They initially filled out functionality that was not available in the Moog modular line - variable formant filtering, ring modulation, and sample & hold.
I added some close up pictures to the auctions so you can check the modules out in detail. Let me know if you have any questions.