Apollo Block I Overcurrent Sensor, measuring 4″ x 3.75″ x 3″, with a Planautics Corp. tag on the side, reading: "Switch, Power Transfer, Motorized, NAA Cont. No. ME-452-0026-0001, Mfg. Ser No. 100494090008, Mfg. Part No. M-201-3-5." The opposite side bears a circuit wiring diagram, and a port on the top marked "J1" is covered with a yellow cap. In fine condition.