The following companies made non-match USGI M14 rear sight elevation and windage knobs in the 1960s. The M14 elevation knob was marked with "M" to denote in calibration in meters. This is an item of ongoing research.
Elevation knob and pinion assembly
Druge Brothers - DRC
Frazier Manufacturing - FZR, made in 1962
Globe Union - made in 1962, possibly later
New Haven Clock - NHC, made in 1965
Springfield Armory - made in 1959, possibly later
Wico Electric - WCE, made for H&R and TRW and in 1969 as replacement spares
Windage knob assembly
Bruce Machine and Engineering - BME, made for Springfield Armory
Druge Brothers - DRC
Frazier Manufacturing - FZR
Stewart Iron Works - SWK
Weather Manufacturing - W inside a hexagon
Wico Electric - WCE
Wright Manufacturing - HRA-W, made for H&R
Wright Manufacturing - WRIGHT, made for TRW