It's a Homelink transmitter used by a lot of different manufacturers.
It is self contained and hard wired to the car, that's what you see going into the mounting rod. The unit has about .25" of electronics sunk into the headliner. These days most mfg's are using the rear view mirror to mount the buttons, you can use them to operate garage doors or anything Homelink connected - maybe like a light in the house.
That's a cool mod - looks great!
Once I had all of that done I test fitted it together
Now I had to route the wiring.
Make sure that you pull the wiring connectors out of the headliner in the donor car. This will be installed up in the headliner of the mustang.
I unpinned the plug and ran the wire through some heat shrink and pulled the mount out of the visit, it's tight but it will pull out. I also used a little bit of smaller heat shrink to run the wire up into the head liner.
i used some glue and clamps to start the reassembly.
I used upholstery thread the a needle and just ran it through the existing holes. Lastly I clamped the silver tabs on the end. The red is hot and grey is ground. The program it i watched a YouTube video.