HI, as we've discussed before on several occassions...for every general rule/policy through the history of VC manufacturing, there is always the possibility of exceptions.
When we talk about vintage watches, none of the manufacturers, retailers or customers ever expected that end-users would ever see the inside of these watches. The only people expected to see what was inside were the watchmakers that would provide maintenance/service.
This is why these guidelines that we collectors today have discovered by studying vintage watches and history are never absolute. There is always room for exceptions and things to be discovered later on. This is true of history, science, and life
For the two watches that you showed, as long as the serial numbers between the movements and cases can be confirmed by VC to be a proper match (and not faked)....any other detail is much less significant.
I have a Ref. 6340 from 1965 with the same maker's mark as SteveG's Ref. 6340. Mine has the number engraved on the case, his does not.
The same can be said for the engraving on other watch you saw on Chrono24.
Not having absolute rules always makes things more difficult to understand, but that's life in general. And VC being 261 years old has lived a very long time and has many examples of this type of "organic" life where not everything is perfectly structured.