You've found something intriguing—but let's clarify a common misconception: standard spirit levels (including bullseye levels) use an air bubble in liquid—not ball bearings. The bubble rises to the highest point to indicate levelness. Ball bearings rolling in glass tubes serve a different purpose entirely.
Based on your description of small glass tubes containing three tiny steel balls, here are the most likely identifications—ranked by probability:
🔍 Most Probable: Vibration Indicator or "Rattle Test" Capsule
Those Glass Tubes with Ball Bearings — Likely Not from a Spirit Level (Here's What They Probably Are)
