Transistor NPN Silicon Darlington 40V 0.33A TO-92 Pre-amp Medium Speed Switch
 
The NTE172A is a silicon NPN Darlington transistor in a TO92 type case designed for preamplifier input stages requiring input impedances of several megohms or extremely low level, high gain, low noise amplifier applications.
 
Full spec sheet:
https://www.nteinc.com/specs/100to199/pdf/nte172a.pdf