It's not like that for Carreras. Autavias were carrying signed crowns long before they started on the Carreras, whether 12s or 45s. Certainly none of the Carreras were introduced with signed crowns in first execution and we don't see every example being fitted with a signed crown until, as I said earlier, the second execution.

We do see a number of first execution Carreras with signed crowns and I think some of these are factory fitted, but I think some are also later additions. Certainly if a watch was going back to the factory for revision that required a new crown post about 1970, a signed one was fitted as the unsigned ones no longer appeared to be stocked.

Take a look at some of the signed crowns fitted to early Carreras - sometimes they are thicker than they should be, and these ones look to have found their way from Autavias onto Carreras. I believe the stem and tube are the same diameter for both watches, but the crown is physically thicker for the Autavia to match the larger watch.

As a personal rule of thumb, I am generally happy to take an unsigned crown on an early Carrera at face value, but if the crown is signed, I will look more closely to see if I can tell it is original.