fittings
A plastic or metal frame surrounding the tube
Signs that the tube was once attached to another object
Similar items in the same collection
A tube by itself may be difficult to identify, but its original housing could provide a much stronger clue.
4. A Component from an Older Measuring Device
Some measuring and positioning instruments use small moving elements to show changes in angle or orientation.
A traditional spirit level, for example, uses a liquid-filled tube and an air bubble rather than loose metal balls. However, other types of mechanical indicators may use movable weights or balls.
If
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