2SD1427 silicon NPN transistor with damper diode by Toshiba. Package: TO3-P(H)(BS) package - ugly looking thing Download Toshiba 2SD1427 datasheet: Status: NOS (New Old Stock) (Note: these always test as 2 x common cathode diode if tested on Peak DCA74, this is nornmal) (resistance between Emitter & Base stated as 50 Ohms, usually tests as about 40 Ohms) RoHS compliant: no