This part is a kind of semiconductor called S8550.

Function of this product has LOW VOLTAGE HIGH CURRENT SMALL SIGNAL PNP TRANSISTOR.

Manufacturers : UTC

Image and pinout :

Some of the text within the PDF file :

UNISONIC TECHNOLOGIES CO., LTD S8550 PNP SILICON TRANSISTOR LOW VOLTAGE HIGH CURRENT SMALL SIGNAL PNP TRANSISTOR  DESCRIPTION The UTC S8550 is a low voltage high current small signal PNP transistor, designed for Class B push-pull audio amplifier and general purpose applications.  FEATURES * Collector current up to 700mA * Collector-Emitter voltage up to 20 V * Complementary to UTC S8050 1 TO-92  ORDERING INFORMATION Order Number Lead Free Plating Halogen Free S8550L-x-T92-B S8550G-x-T92-B S8550L-x-T92-K S8550G-x-T92-K Package TO-92 TO-92 Pin Assignment 123 EBC EBC Packing Tape Box Bulk  MARKING www.unisonic.com.tw Copyright © 2014 Unisonic Technologies Co., Ltd 1 of 4 QW-R201-014. E S8550 PNP SILICON TRANSISTOR  ABSOLUTE MAXIMUM RATING (TA=25°C, unle [ ... ]

S8550 PDF Datasheet Download