Armando is spot on, the registers have a different paint than the rest of the dial. It's the case for the majority of 70s Heuers - the Silverstones spring to mind as an exception, but not too many others. Champagne Carreras too. But really not too many others (I'll stop the train of thought before I reach too long a list of exceptions!).

In this case, the registers do look slightly faded to me too - they wouldn't have been that light grey originally. But the registers are typically in a matte paint, whereas many of the dials have a metallic finish and that seems to be a lot harder to make photochromatically stable than matte finishes (although an 80s car in a solid red finish will almost always have a tendency to go pink with time, so not all solid finishes are immune. Interestingly, 70s cars in solid red often went orange instead of pink. I imagine dial paint, much like car paint, has changed a lot over the decades too). There are some exceptions to this too - by the time of the Carreras with the yachting indicators, the metallic blue dial finish is pretty stable but the matte registers have a strong tendency to bubble and show white flecks through the black.

The remarkable thing about this eBay watch is how evenly it has faded - looks not to have been moved for a long time and have been presented squarely face on to the sun. Nice effect and up to the potential purchasers to decide how much that affects value.

There was a more or less contemporary charcoal-dialled Carrera recently on eBay too, but that had faded to a mix of coppers and browns much like the "paintless" Monacos. It's quite unusual for the effect to be as even as on this Autavia, with the exception of the later blue dials that fade to lilac - that seems routinely to happen pretty evenly.