Video inputs Tube TV

[ARC Tech-109]

Does anyone recall what the chassis or model was of a late 60s vintage RCA that had the SO-239 video in/out & 8-pin jacks used by schools and the like? I had one years ago that was used with a Panasonic EIAJ format and I recall some of the big ugly presentation Something Carlson 25" B&W with big knobs and speakers had a video I/O jacks. What I'm specifically looking for is the interface circuit they used to bring the video in behind the detector and sound trap to use in my Magnavox T940 and maybe someone knows of other models that had the video in/out.
I was the A/V geek in school during the 80s and spent plenty of time messing around with these but for the life if me I can't remember the models. The RCA was a metal cabinet 20-something inch and the Something Carlson was a big wood affair we called the "rolling tombstone" being so big and bolted to a tall wheeled cart with a Panasonic NV-3020 EIAJ... we were slightly behind the times and didn't get anything VHS until around 1983 and that got us some of the XL-100 Lyceum sets.
I've spent the better part of an evening looking for potential tube sets with the video in/out but keep striking out, anyone maybe have any ideas?

Thanks
Brett