ITE industrial circuit line breaker switch. We were told that ITE is a division of Siemens. This breaker is marked 200 on the side of the switch lever. It measures about 7" x 3" x 3" and takes 2 legs. We're not sure of the voltage for this breaker (probably 600 volts?), but it doesn't seem to be marked.

We've tested this breaker with a ohmmeter for continuity between the terminals with the breaker open and closed and it tests with 0 ohms (no notable resistance with the breaker closed) and 1 (infinite resistance with the breaker open).