Text in force at 23-63: from 23-33, effective 11 Aug 1986.
[(a) Flap and landing gear] control knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions) in the following figure: Flap Control Knob Landing Gear Control Knob [(b) Powerplant control knobs must conform to the general shapes (but not necessarily the exact sizes of specific proportions) in the following figure: Power (thrust) Control Knob RPM Control Knob Mixture Control Knob Carb Heat or Alternate Air Control Knob Supercharger Control Knob]
51 FR 26657 · Source