A magnetic latch for a display of a laptop computer is disclosed. With an application running in the POS terminal apparatus, a device manager determines whether the external device is capable of counting a first value indicating a usage amount of the external device, and if so, the device manager acquires the first value from the external device in response to a first command from the application. The sled appendages permit the probe to contact and ride along the surface of the structure and are rotatably connected and curved away from the surface of the structure to compensate for contoured surfaces and inspection around holes and edges.