2SD1555 TOSHIBA, Silicon NPN+Di power Transistor, 
Vcbo 1500V, Vceo 600V, Vebo 5V, Ic 5A, Tc 25°C 50W, 3MHz, tf 0.5µs  
Case type: SOT-93, TO-3PF ISOL,
Marking: D1555, 
BCE
2SD1555 = S2055N, S2055AF,