600k serial would clear up most doubt. The dial, hands, insert etc could work with the replacement caseback from 1971. Still odd as the thread starter continues to say 6m even after it is pointed out. Let’s see those full engravings. And the documentation..
If 6m I would like to see some sort of Rolex papers explaining the case. Otherwise I would start thinking the case is non-Rolex.
My previous 6542’s were more in 3-500k serial bit they did not have STAINLESS STEEL beside the serial. Of vourse 600k is later but just saying.