This part is a kind of semiconductor called 2N3668.

Function of this product has SILICON CONTROLLED RECTFIERS.

Manufacturers : Digitron Semiconductors

Image and pinout :

Some of the text within the PDF file :

2N3668-2N3670, 2N4103 High-reliability discrete products and engineering services since 1977 SILICON CONTROLLED RECTFIERS 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 Rating Symbol Non-repetitive peak reverse voltage VRM Peak repetitive reverse voltage VRRM Peak forward blocking voltage Forward current for case temperature TC = +80°C @ average DC value at a conduction angle of 180° RMS value Peak surge current for one cycle of applied voltage 60 Hz (sinusoidal), TC = 80°C 50 Hz (sinusoidal), TC = 80°C Fusing current (TJ = -40 to +100°C, t = 1 to 8.3ms) VFBOM IFAV IFRMS IFM I2t [ ... ]

2N3668 PDF Datasheet Download