In high-vibration environments (e.g., machinery), bubbles can be hard to read.
Ball bearings provide a clear, physical indicator of gravity’s pull.
Some antique levels used three balls to triangulate levelness more precisely.
Where You Might Find These:
Inside an old wooden or metal leveling tool (often brass or cast iron)
In a machinist’s toolbox
At estate sales, flea markets, or inherited workshop drawers
If the glass tube is dome-shaped, sealed, and mounted in a metal ring, it was almost certainly part of a leveling instrument.
⚠️ Safety Note:
The liquid inside may be ethanol, oil, or historically, even ether—some older fluids can be flammable or toxic.
