DescriptionIncluded is a description card from the Transistor Museum that says, "
Device ID: Fairchild 2N4124 transistor
Type: Silicon NPN diffused planar epitaxial
Case Color/Style: Black plastic TO-92
Vintage/Date Code: 1960s/1970s
Use: General purpose amplifier/switch
Notes: TO-92 plastic case was first used in mid 1960s. This model is an early example."