This part is a kind of semiconductor called BT137-600E.

Function of this product has Triac.

Manufacturers : BLUE ROCKET ELECTRONICS

Image and pinout :

Some of the text within the PDF file :

BT137 Rev.E Mar.-2016 DATA SHEET 描述 / Descriptions TO-220 塑封封装 双向可控硅。Triac in a TO-220 Plastic Package.  特征 / Features 采用玻璃钝化技术，采用环氧塑脂塑料封装，四个信号区都可以满足高灵敏度需要。 glass passivated,sensitive gate triacs in a plastic envelope，where high sensitivity is required in all four quadrants. 用途 / Applications 用于一般双向开关和相位控制。 Use in general purpose bidirectional switching and phase control applications. 内部等效电路 / Equivalent Circuit 引脚排列 / Pinning 12 3 PIN1：Main Terminal 1 PIN 2：Main Terminal 2 PIN 3：Gate 放大及印章代码 / hFE Classifications & Marking 见印章说明。See Marking Instructions. http://www.fsbrec.com 1/6 BT137 Re [ ... ]

BT137-600E PDF Datasheet Download