Mine was first run in 1981 according to the scribing on the inside of the control cover.

I think they are good units. more complicated than todays units but seem rather robust since they were built for 500 psi. The extra flow meters are very handy to gauge the unit and membrane status. I plan on keeping this one around for a long while. Just don't like the loudness of the unit.

The RO is stuck in a corner right now; behind a bunch of stuff as we are in the process of getting ready to build a walkin cooler for the syrup barrels. It may be a bit for pics. I will look in the book to see if there are any schematics