Help!! What is this box?

With a '75 Manual there 's at least a couple approaches.
Knowing nothing about the wiring, one approach is if its the engine bay to look at the CE diagrams and see which ones match. It's only a couple pages and the drawings are pretty clear.
Another approach is to look at the wire insulation colors (and sizes) to see which circuits it might be. It may be neccessary to wipe some of the grime off the wires. The manual has list of circuit names matched to the colors. Bugman posted a photo of it from '75 in post 26 this thread.
https://www.forabodiesonly.com/mopar/threads/ignition-help-needed-stumped.499412/post-1973584589Combining the two ofcourse is also possible.

The more you do, the more you learn.

The post was about using the search feature on the forum to identify the part. What would he have typed in to search for it? Thingamajig? Doohickey?

Maybe the guy didn't know he could have gone to mymopar to get a manual? He could have thought they had to be purchased online with a week wait time for the mail to get here? I'm sure he assumed that the question would be safe to ask on a forum where hundreds of questions are asked and answered every week. 99% of the questions here could simply be solved with a "Use the search function and go buy a manual" response but that would make for a pretty boring forum.

You obviously flunked the hell out of comprehension but no one had been grouchy.

I've been around long enough to know your schtick. You can be very helpful or you can be a passive aggressive grouch and then gaslight people when they call you on it. I don't know if it's bi polar or old age but you do you man. My reading comprehension is just fine.