Submariner Flat Four

[Rocky_24]

Hi guys,
I've been looking for some information in various threads for some time but haven't found a pleasant answer so far: Were the flat 4s on black Submariner bezels made randomly throughout the years or was there a certain period of time when these were exclusively made for particular references? I've seen 14060s, some SDs and so on both with pointy and flat 4s, so I'm not sure whether their bezels had been replaced or some simply got different 4s on their bezels than others of the same reference / production.
Maybe some of you know more about that (except for the 16610LV - I know about this one).