camper special horn on the roof of the cab

[rajincajintj]

my "new to me" truck has a horn on the roof of the cab.

i REALLY want this thing to work.



inside there is a lever that looks like it would actuate the horn with a chain attached or something.



now i have a couple questions and i am really warry (especially with all the rain we are having) taking it off and investigating anything on the roof with the potential for leaks

AND after getting my haynes manual and factory service manual there is no informaiton in there about it either.

soooooooo

can anyone shed any light on what this thing is, how it operates and how i can plumb to it? i assume its air operated but i have no air on board yet.

thanks