Dual decay envelope (4HP)
Percall by Befaco.
My own version of the envelope section in Befaco's Percall, identical in function to (part of) the original.
The first PCB has the Decay potentiometers wired in reverse, turning clockwise reduces decay time unlike what the panel graphic suggests (or what was intended).
It may also be a good idea to kludge in some protection diodes for the trigger transistors.