I found this in my MIL's treadle cabinet. I think I remember seeing something like it when taking Home Ec way back when....If acts almost like a compass, the magnetic thing twists when it is near metal.
The only markings on it are a little devil face on both sides.

Anybody know???

OK, now I'm curious too. I hope someon the board identifies it.
From one Montanan to another - Howdy!

looks like an old stud finder to me..I remember my DAD had one similar to it

That was my hubby's guess too!

Yep, that's what it is. Nothing to do with the treadle.....

Well, what in heck was it doing in *her* sewing machine, don't you wonder?! :?

Jan in VA

That's pretty cool! I could use it! Want to put up shelves in sewing room. Son says u have to find the studs. Me: ookkaaayyy.... Lol

Interesting. My guess is though it's only going to work where there is metal driven into the stud...so you will have to find somewhere where there is a drywall nail or screw. If you're in a newer house, modern drywall (1960 or so & later), look along the 4' height along the wall, where the joint is. If you have plastered walls good luck, as all the metal mesh underneath, won't help you find a stud with a magnet.
Thanks for sharing "this old tool"; I love things like this.

Maybe she was looking for a "stud" (2 legged kind! lol)

Good answer!