M55629/1-043 is a single-pole magnetic unsealed circuit breaker with trip-free operation, designed to protect electrical circuits in military applications across a current range of 0.2 to 100 amperes. The breaker features selectable voltage ratings (120 V ac, 240 V ac, and 50 V dc) with multiple tripping-time delay codes (A through T) to accommodate various load characteristics and inrush requirements. It incorporates high-inrush or transient suppression features for delay codes K, L, M, N, P, R, S, and T, with interrupting capacities of 2,000 amperes at 50 V dc, 2,000 amperes at 120 V ac (60 Hz), 1,500 amperes at 120 V ac (400 Hz), and 1,000 amperes at 240 V ac. The device is constructed with brass or phosphor bronze terminals and mounting hardware, and meets MIL-PRF-55629/1G specifications. Applications include aircraft electrical systems, military vehicles, shipboard power distribution, and other defense systems requiring reliable circuit protection with precise current and time-delay characteristics.