:Hi Jeff, thanks a lot for the very thorough investigation (and a lot of envy for most of your nice 5100's, though I'm quite familiar with that pewter one by now!).
I have come to the same conclusion, and think that it can be an effect of the overall black surrounding if chrono hands tend sometimes to appear reddish on the 510.501 and the 510.511.
In fact on the lighter ones like the pewter 510.503 hands look a light orange even on NOS or mint items.

Catalogues have been definitely misleading this time. And by the way...has anyone notiched that 5100 Carreras (and the Cortina, for that matter) do not seem to have any tachymetre ring in the picture?