This part is a kind of semiconductor called BT137.

Function of this product has 8A TRIAC.

Manufacturers : KCD

Image and pinout :

Some of the text within the PDF file :

 Description: High current density due to mesa technology;Glass Passivation.  Applications BT137 series triacs is suitable for general purpose AC switching. They can be used as an ON/OFF Function in applications such as static relays,heating regulation,induction motor stating circuits... or for phase contol operation light dimmers,motor speed controllers.  Features: Blocking voltage to 600 & 800V On-state RMS current to 8A Non-repetitive peak on-state current to 71A  Absolute Maximum Ratings Symbol Parameter VDRM Repetitive peak off-state voltage VRRM Repetitive peak Reverse voltage IT(RMS) RMS on-state current (full sine wave) Non-repetitive surge peak On-state current ITSM (full cycle,Tj=25℃) I2t I2t Value for fusing Conditions TJ=25℃ TJ=25℃ Tc=110℃ f=60Hz,tp= [ ... ]

BT137 PDF Datasheet Download