This part is a kind of semiconductor called 2SD426.
Function of this product has (2SD425 / 2SD426) 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 2SD425 2SD426 DESCRIPTION ·With TO-3 package ·Complement to type 2SB555/556 ·High power dissipation APPLICATIONS ·Power amplifier applications ·Recommended for high-power high-fidelity audio frequency amplifier output stage PINNING(see Fig.2) PIN 1 2 3 Base Emitter Collector Fig.1 simplified outline (TO-3) and symbol DESCRIPTION Absolute maximum ratings(Ta= ) www.DataSheet.co.kr SYMBOL PARAMETER 2SD425 CONDITIONS VALUE 140 UNIT VCBO Collector-base voltage 2SD426 2SD425 Open emitter 120 140 Open base 2SD426 120 Open collector 5 12 12 TC=25 100 150 -65~150 V VCEO Collector-emitter voltage V VEBO IC IE PC Tj Tstg Emitter-base voltage Collector current Emitter current Collector power dissipation [ ... ]