Identifying Small Glass Tubes Containing Three Tiny Ball Bearings: What Could They Be?

Is it safe to open the glass tube?

It is best not to open it. The glass may break, and the contents or internal materials may be unknown. If it is sealed, leave it intact until its identity is established.
What is the best way to identify it?

Start with clear photographs, accurate measurements, and observations about whether the balls move. Include any markings and information about where the object was found. These details can help a specialist narrow down the possibilities.
The Best Way to Identify Your Glass Tube

A small glass tube containing three tiny metal balls is