Not sure when the Schuemann system was first available. In a quick search, I found what looks like an early ad for it in Soaring in 1973. We were using a tail venturi in the early 1970s. Wil was playing around with water ballast in his 301 Libelle before then and then diagnosing the drag chute deployment problem in his ASW 12 after that. But I'm almost certain the SunShip Game came before the Schuemann box. So: diaphragm compensator is my best guess: likely a PZL.

Chip Bearden
JB