This part is a kind of semiconductor called BD137.
Function of this product has NPN Epitaxial Silicon Transistor.
Manufacturers : Fairchild Semiconductor
Image and pinout :
Some of the text within the PDF file :
BD135 / 137 / 139 — NPN Epitaxial Silicon Transistor BD135 / 137 / 139 NPN Epitaxial Silicon Transistor August 2013 Features • Complement to BD136, BD138 and BD140 respectively Applications • Medium Power Linear and Switching 1 TO-126 1. Emitter 2.Collector 3.Base Ordering Information Part Number BD13516S BD1356STU BD13510STU BD13516STU BD13716STU BD13710STU BD13716S BD13916STU BD13910S BD13916S BD1396STU BD13910STU Marking BD135-16 BD135-6 BD135-10 BD135-16 BD137-16 BD137-10 BD137-16 BD139-16 BD139-10 BD139-16 BD139-6 BD139-10 Package TO-126 3L Packing Method Bulk Rail Bulk Rail Bulk Rail © 2007 Fairchild Semiconductor Corporation BD135 / 137 / 139 Rev. 1.2.0 1 www.fairchildsemi.com BD135 / 137 / 139 — Features Absolute Maximum Ratings Stresses exceeding the absolut [ ... ]