This part is a kind of semiconductor called P6KE51A.

Function of this product has ZENER OVERVOLTAGE TRANSIENTSUPPRESSORS.

Manufacturers : Motorola Inc

Image and pinout :

Some of the text within the PDF file :

MOTOROLA SEMICONDUCTOR TECHNICAL DATA Zener Transient Voltage Suppressors Undirectional and Bidirectional The P6KE6.8A series is designed to protect voltage sensitive components from high voltage, high energy transients. They have excellent clamping capability, high surge capability, low zener impedance and fast response time. The P6KE6.8A series is supplied in Motorola’s exclusive, cost-effective, highly reliable Surmetic axial leaded package and is ideally-suited for use in communication systems, numerical controls, process controls, medical equipment, business machines, power supplies and many other industrial/ consumer applications. Specification Features: • Standard Zener Voltage Range — 6.8 to 200 Volts • Peak Power — 600 Watts @ 1 ms • Maximum Clamp Voltage @ Peak Puls [ ... ]

P6KE51A PDF Datasheet Download