This part is a kind of semiconductor called 2SD555.

Function of this product has Silicon NPN Power Transistors.

Manufacturers : SavantIC

Image and pinout :

Some of the text within the PDF file :

SavantIC Semiconductor Product Specification Silicon NPN Power Transistors 2SD555 DESCRIPTION ·With TO-3 package ·High power dissipation ·Complement to type 2SB600 APPLICATIONS speed ,high current ,high power applications PINNING(see Fig.2) PIN 1 2 3 Base Emitter Collector Fig.1 simplified outline (TO-3) and symbol DESCRIPTION ·For high Absolute maximum ratings(Ta= ) SYMBOL VCBO VCEO VEBO IC PC Tj Tstg PARAMETER Collector-base voltage Collector-emitter voltage Emitter-base voltage Collector current Collector power dissipation Junction temperature Storage temperature TC=25 CONDITIONS Open emitter Open base Open collector VALUE 250 200 5 10 200 150 -55~200 UNIT V V V A W THERMAL CHARACTERISTICS SYMBOL Rth j-C PARAMETER Thermal resistance junction to case VALUE [ ... ]

2SD555 PDF Datasheet Download