A replacement encoder knob compatible with a wide range of Rohde & Schwarz test equipment from the 2000s onward including the SMJ signal generator, the AMU baseband generator, the UPV audio analyzer, and likely many similar vintage instruments. The instruments that use this encoder wheel size that I've seen all have the raised plastic ring around the base of the wheel.

Fits a 6mm round encoder shaft with a press fit, 28mm around and just over 14mm tall. Comparison to an original part in the second picture.

Prusa

I3 MK3S

No

No

125um

30%

Should print fine in most materials, no supports required as long as your bridging related settings are reasonable. Finer layer heights yield better smoothness and fewer noticeable layer lines on the slightly domed top.