Replacement knobs for Nichols Electronics ice cream truck music box

I got a used Nichols Electronics Digital II music box, but it was missing the knobs.  These are replacement knobs based on the dimensions of the knobs I had on my Nichols Electronics Digital.

You will need a printer capable of dual extrusion for this.  It needs to be printed in a filament which can withstand vehicle temperatures if you're going to actually use this in a vehicle.  I used Atomic Filament Metallic Silver PETG for the outer ring and (IIRC) eSUN Black PETG for the centers.  When printed correctly, the knobs are a press-fit on the shafts.  The outer ring is the same for both knobs, but the black center part is different - the song selector shaft is keyed.  For a closer matching texture, be sure to print the top layer of the center using Hilbert Curve infill and use Archimedian Chords or similar for the outer silver ring.