This is a TYCO (Tyco Electronics / Alcoswitch) black plastic control knob with a brushed aluminum / silver metal insert top and a scalloped (fluted) outer grip.
 It includes a set screw with a brass insert for secure mounting on a potentiometer shaft (likely 1/4" based on similar TYCO/Alco models).
The design is a classic industrial-style knob commonly used on electronic test equipment, audio gear, amplifiers, effects pedals, radios, and other control panels from the 1970s–1980s era.
 TYCO / Alcoswitch produced many similar knobs (e.g., series like PKN, PKES, or PKJ) for OEM and replacement use.

Scalloped grip design and set screw mounting with brass insert.
Produced circa 1970s-1980s in the United States.
Ships from PHX.
Please review the photos carefully as they form part of the description.
Thanks for looking!