This part is a kind of semiconductor called 1N5987.

Function of this product has 500mW ZENER DIODES.

Manufacturers : Digitron Semiconductors

Image and pinout :

Some of the text within the PDF file :

1N5985-1N6031 High-reliability discrete products and engineering services since 1977 500mW ZENER DIODES FEATURES  Available as “HR” (high reliability) screened per MIL-PRF-19500, JANTX level. Add “HR” suffix to base part number.  Available as non-RoHS (Sn/Pb plating), standard, and as RoHS by adding “-PBF” suffix. MAXIMUM RATINGS Operating and Storage Temperature DC Power Dissipation @ 25°C Lead Length 3/8” Derate above 50°C Forward Voltage @ 200mA -65 to +175°C 500 mW 3.33 mW/°C 1.1 V ELECTRICAL CHARACTERISTICS (TA = 25°C unless otherwise specified) Part Number Nominal Zener Voltage VZ @ IZT (note 2) Volts Zener Test Current IZT mA Maximum Zener Impedance (note 1) ZZT @ IZT Ohms ZZK @ IZK = 0.25mA Ohms B,C,D Suffix A, NonSuffix B,C,D Suffix A, NonS [ ... ]

1N5987 PDF Datasheet Download