I have never
seen that mounting frame for the front panel, but perhaps
it's related to your "DEC DataSystem" cover panel.
I've seen that sort of frame a couple of times; they were used in
(possibly among other things) embedded applications. It's been a long
time but I think I saw them in big GenRad board testers.
> Here's a photo I found googling around for "DEC Datasystem"
>
>
That could explain the original purpose of the 11/34 in my possession, the
rack that the system came in has a DEC DataSystem panel: