Module 316

 PPG 300 Series Modular System 316 Frequency-Envelope Follower Module

 

The 316 is an interesting module, combining both frequency to voltage conversion along with an envelope follower and gate extractor. Also included is a "gate switch" and "fuzz" output.
Wolfgang states in his recollections that the pitch to voltage circuit was one of his designs that predated many of his products. If you have this module, please get in touch!