Version: -300/ pax/ wheel

What is the yellow band for on the LH PROP RPM between 20-50%?

 

 

Looks like the "less than ideal prop rpm zone".
appears they missed it or it's a replacement gauge, for realism

 

The left one is apparently indeed not an original Twin Otter gauge, but this is exactly how the instrument panel looked in the reference plane that is used to create the Aerosoft Twin Otter.

I think it gives it a bit more authentic flavour this way

and was the reason that the yellow did not appear on both gauges.....copied from the reference a/c

Yes, that was how it looked. I think the image is in the manual actually.