Big lot NOS knobs - Polished aluminum pointer-line inset. These have a good quality feel to them. A wide variety of consumer and industrial electronics used knobs like these in cases where the shafts were of the push-on "D" style. (note: some of the photos may appear to show a yellowed inset disc on some knobs, but these pics were shot outside and that's an aftereffect of reflections)

Some 1970s Ampex equipment comes to mind, some hi-fi, radios, tuning and test gear, etc. Several of the discs may have minor imperfections, marring or marks from knocking against other knobs in the box over the years. see close-ups! 

From a bulk supply we acquired from liquidator surplus. 

A good way to finish off your amplifier restoration or custom project. No reserve - high bid takes the lot of 40! best of luck!