This part is a kind of semiconductor called 1N5938A.

Function of this product has 1.5 WATT ZENER DIODES.

Manufacturers : Digitron Semiconductors

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Some of the text within the PDF file :

1N5913A-1N5956A High-reliability discrete products and engineering services since 1977 1.5 WATT 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 Characteristic Symbol DC power dissipation @ TL = 25°C Maximum forward voltage @ IF = 200 mA Maximum thermal resistance junction to ambient air Note 1 PD VF RθJA Junction temperature range TJ Storage temperature range Tstg Note 1: Valid provided that leads are kept at ambient temperature at a distance of 10 mm from case Value 1.5 1.2 120 -65 to +175 -65 to +175 Unit Watts Volts °C/W °C °C ELECTRICAL CHARACTERISTICS (TA = [ ... ]

1N5938A PDF Datasheet Download