Abstract: An electromagnetic counter with a rotary counter and an electromagnetic operator for indexing the counter having a generally U-shaped core plate mounted in opposed pockets in parallel end supports of a plastic support frame, an energizing winding on one of the parallel legs of the core plate, and a pivotal actuator connected for indexing the counter having a ferromagnetic armature member positioned aside and extending transversely of the parallel legs of the core plate. A ferromagnetic insert having a preselected configuration and permeability is inserted through a slot in the support frame and press fit between the parallel legs of the core plate to provide a saturable magnetic shunt for preventing electromagnetic operation of the counter by electrical noise spikes of relatively short duration and to provide an air gap filler for reducing the incipient air gap of the electromagnet.