The comparator is a measuring instrument used for linear displacement measurements.
The instrument operates by reading the movement of a moving cylindrical rod that slides inside a tubular guide. The end of the rod (called feeler pin or tracer point) touches the surface of the object that is being tested.
A spring constantly pushes the arm outwards the comparator body, thus ensuring that the feeler pin is continuously in contact with the object under exam.
When the surface moves in the direction of the axis of the arm (moving closer or further away), the arm also moves. A reading system amplifies and displays this movement making the measurement available.
In working order, good condition and without damages.