Retro is right. is is the worlds best studfinder. to me far better than the electronic ones. the magnet it in will hold the thing on the wall over a nail for screw.
ten bucks on amazon.
tom
2002 45'8" Newell Coach 608 Series 60 DDEC4/Allison World 6 Speed HD4000MH
Lol, after Jimmy said "check valve" I thought yes thats what it is!! I saw some scratches on the bottom that made it look like it was possibly dragged on something like a wall and thought maybe it is!! There is so many different kinds but Ive never seen one like it
Love old school
1976 Newell 8.3 cummins allison 6spd
1977 Newell 8.3 cummins allison 6spd