This part is a kind of semiconductor called SM24.

Function of this product has Transient Voltage Suppressor 500 Watt.

Manufacturers : Micro Commercial Components

Image and pinout :

Some of the text within the PDF file :

MCC Features l l l l l
  omponents 21201 Itasca Street Chatsworth    !"# $ %    !"# SM03 THRU SM36 Transient Voltage Suppressor 500 Watt SOT-23 A D SOT-23 Package For surface mount application Protects 3.0/3.3 up through 36V Components Protects 2 Unidirectional or 1 Bidirectional line Provides electrically isolated protection Tape & Reel EIA Standard 481. Mechanical Data l l l l Molded: SOT-23 Surface Mount Body marked with device number. Mounting Position: Any Weight: 0.14 grams (approx.) F C B MAXIMUM RATINGS § § § § Operating Temperature: -55 C to +150 C Storage Temperature: -55oC to +150oC SM03 thru SM36 have a Peak Pulse Power:500 Watts (8/20 usec, Figure 1) Pulse Repetition Rate: <.01% o o G E H J DIMENSIONS INCHES [ ... ]

SM24 PDF Datasheet Download