The case is from a group buy run by Protozoa Studio, and designed to fit a Discipline PCB.
I designed a new PCB (and plate), which uses the same ATMega32a and a very similar circuit but redesigned (from scratch) to fit an ortholinear layout while still being compatible with the case – smellycoat.
The big knob is set up with a smooth (ie no detent) encoder which complements the extra weight nicely.
It's set up for scrolling at the moment but I'm going to add some different functions for different layers.
To be honest they feel kinda shitty with a normal knob (a little rough and scratchy) and don't spin very freely, but with that massive heavy knob you don't notice the scratchiness and the extra weight helps it spin.
And the knob itself is on sale e.g. here and here.
The other two knobs control volume and undo/redo, and have a more usual detent decoder.
Finally, here's another pic showing off the exposed components a bit better: