This module is in excellent condition. kept in a smoke free studio with a little bit of rack rash. 
Had this as my first envelope. great classical adsr perfect for a new system (as I did) or if you just need a couple of envelopes for your system.  
It is now discontinued so pretty rare as only limited models exist!

DUAL ADSR is a twin ADSR envelope module. In addition to the four common parameters, Attack, Decay, Sustain and Release, the module offers a “Hold” phase that follows the Attack phase. By this, sounds with short decay and low sustain level can achieve additional punch

Both envelopes work independently but can be triggered over Gate Input 1 with Gate 2 unpatched. The unit also offers Gate-Inputs from the system-bus allowing you to trigger the envelopes from an appropriate MIDI/CV-interface without front patching.

Typically, both envelopes work with logarithmic characteristics. However, a switch allows to change the character of one selectable envelope to linear.

Both envelopes offer two parallel outputs each. In many case this makes the use of multiples superfluous.

The module has a width of 60 mm  (12 HP).