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:
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.”
Tandberg also had a graphics option for some of their terminals. This option supported Tek-style graphics commands, but with the coordinates scaled down to 720x336. I assume this is similar to what other vendors did.
I found a PDF describing the graphics option for the TDV2200S here.
Aha - I see then that PLOT-10 is a standard software library from Tektronix for making graphics happen on compatible output devices. Here’s a brochure:
PLOT-lO/Advanced Graphing software is a complete set of subroutines for fulfillment of real graphing needs in the wide range of problems encountered in today’s business, scientific, and engineering environments. All PLOT-10 Advanced Graphing modules are written in FORTRAN IV and designed to generate a variety of common plots, as well as some specialized graphs, without involving the user in the programming details.
