The later model is, the less chance to get some more information,
if the watch isn't exceptional.
Back in the 40's, some years only a few hundred watches were made.
I know some year's production figures.
1932 only 211 movements were made!
I have the watch presented below, made in 1937,
a year they made 439 watches,
even though they had a production capacity of 3000 !
So naturally they had more control over when and where,
and to whom, their watches were sold.
How exclusive, complicated, special or rare a watch was,
when it was made, and sometimes also to whom it were made,
of course, also means that more information was kept.
The most exspensive Vacheron&Constantin, so far, sold at an auction,
"King Fouad" supercomplicated pocket watch from 1929, for 2.777.250 $,
has every document conserning it.
The same goes for the most exspensive new produced wristwach.
VacheronConstantin Tour de l'Ille from 2005, at 1.413.000 $.
Both watches were sold at "The Quarter of Millennium of Vacheron Constantin",
at Antiquorum, 2005, an auction I had the honour of being present at :-)