Backcase of the one with the faded bezel is engraved. That is a weird one as it fits the pattern of early case and early bezel, but later pushers and hands. The guy who sold it told me his father got it as a retirement present after leaving Alfa Romeo. No evidence with that, but my instinct was he might have been telling the truth. Didn't ask if it had gone for service or not.

The other two are plain back cases, which fit with the later style models.