Hi Andy,
in their books, they have the exact date of manufacture, as I said, which has nothing to do with the date stamped onto the back of the cases. David Seyffer gave me an example of watch movements (not Mk 11´s) manufactured years before they were sold.
It´s a pity Jürgen King, whose knowledge must be far superior to David Seyffert´s, left IWC saying, there will be no help from him again, ever. He´d be the man to ask any specific questions on vintage IWC watches and movements.
He was apparantly the only man who could distinguish a fake Mk 9 from a real one, but he left IWC and the museum without leaving his knowledge in written form, a pity.