Part Number : D1557
Function :3DD1557 / D1557 / Low frequency amplification bipolar transistor
Manufacturer : Jilin Sino-Microelectronics
Pinout : 
Description
V cbo = 1700V
3DD1557 is a high back pressure NPN bipolar power transistor, manufacturing The main technology employed: high-pressure technology mesa, triplet Diffusion of technology, the use of plastic full encapsulation structure.
Reference Site :
http://monitor.espec.ws/section27/topic78212.html
Datasheet PDF Download
Other datasheets in the file : 3DD1557, D1557