Following on from discussion in the album of pictures from this year’s VCFMidwest thread:
The snap below is from this video, about 8½ minutes in, where we learn that the exhibitor is Gavin, he’s brought a PDP11/23, and is showing Tek graphics not only on the ADM-3A (just about visible) but also on a VT100:
Indeed, more about this machine from Gavin here:
Edit: from a comment in that video, we find the thread where Gavin acquires this kit and gets it running. The images in the head post have gone missing, but they are re-linked further down the page.
Edit: from that thread “I wasn’t able to get all of the sand out from the bottom of the drive, but at this point none of it should be able to find its way into the disk.”