Anyone have any ideas what this thing is? In my limited time, I couldn't get a better photo of the card handles, but at some point, I'll try to do that.
Very interesting finds, Vince! Thank you! Maybe Al can scan that manual at some point so I can see if there are interesting things that can be done with this chassis.
Do you have any DD02 to go with it? If not, you may be restricted to 16 12 bit words, if I understand correctly the manual that Al scanned. There are apparently quad height boards that go in there to provide 12 bits of either input or output. I only see the first four slots implemented there, though.
Also, if those are M623 in C1 and D1, it is the Posibus version.
Do you have any of the screw terminal assemblies to go with it? How about the funky boards with the 2 sockets on top or the ones with two edge connectors to go in them?
Seems I'm missing the I/O and filter assemblies, but those shouldn't be hard to recreate. But yes, this is definitely the Posibus version.
192 bits would be plenty to control a two-manual organ, but you could control one more efficiently (and thus a much larger organ) with some extra circuitry. I'm still trying to understand more about how Prentiss Knowlton interfaced his PDP-8 to the organ back in the day.