Well two good guesses up there
1: OTA antenna amplifier.. If you do not have either a matrix switch (Box of many buttons) with a POWER button. or a wall plate with teh 12 volt outlet, antenna connection, switch and light. or a Sensar Pro. that's a good chance.
2: Satellite antenna (rooftop dome) you will have a Dome up there.
The lack of "Winegard" on the switch suggests a dome.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times