Abstract: A micro hardness testing device (durometer) comprises a permanent magnet having a plunger. A spring arrangement has at least one strain gauge that provides a signal on bending of the spring arrangement. The spring arrangement is carried by the plunger. A penetration body is loadable via the spring arrangement, and the plunger is connected to a current supply. The strain gauge signal is converted to an electrical signal as a measuring signal for the force applied to the penetration body. The measuring signal is supplied to an evaluation unit. The plunger, the permanent magnet and the spring arrangement are enclosed by a housing adapted for insertion into a revolvable nose piece of a microscope. The housing approximates the shape and dimensions of an objective insert for the microscope. The penetration body is adjustable in an optical axis of the microscope.