logically before the production of 16013 / 16030 case would have begun. (I assumed that modelnrs were applied on the case production line.)
Maybe the serial nr was applied on a completed watch, just before it would have been shipped to its buyer (or AD). And with both unsold 1601's, and 16013 models already completed, maybe that is how they got mixed up?
So does anybody know when a serial is applied? On a case, or on a complete watch?