Just another of those things you get given, over time. It's circa 1976, ex-ADS-10 equipment (which used to be ADS-7, in a confusing switch-over of broadcasting channels, between channels 7 and 10, many years ago, due to differing interstate network ownerships). It could be a model BE-400, but I'm not sure if that's what the BE-400 marking on the rear-panel label means (a model code, or something else). This gadget can read audio-track time code signals and display the time code value over a video picture with adjustable sizing, positioning, video levels, etc.
I hooked up audio out from a video player's SMTPE time code track to the Cannon connector, video from the player into the video in connector, and a monitor to one of the video out sockets, and saw a time code window in the traditional manner on the screen. I presume that the multi-pin connector is for using an external time code reader, and just using this gadget as the display device. The prl/serial switch would appear to switch between the two timecode input sockets (the large multi-pin “data mode” connector and the three-pin Cannon socket). I haven't checked with the 6.25 Hz socket is an input or an output, I didn't connect it to anything. But I'd hazard a guess that it's an input, as the colour framing counter didn't change while the tape was running.
If you're interested in old television equipment, you might also want to look at the page about an old Philips LDH1 camera. It's of a similar vintage. I think I might actually have a use for this for some special jobs, but the video editing equipment that I use for my video production work already has in-built time-code generator/readers.