Hello John,
Very interesting question !
A continuation of our discussion last night....
Actually, I "dunno";
currently there are more hints to me that our cars had the narrow white wall tires right from the beginning, not later.
See here a brochure's pic from the first sales brochure (August 1963);
also the Geneva car (VIN 000001) had narrow white walls - including option code 64/1 on the data card.
But there are also other deviations (wide white walls), e.g. the IAA_1963 pic (Internationale Automobil-Ausstellung, Frankfurt, Autumn 1963);
but mostly these "factory-original" wide-white wall tire cars appear to me mostly to be more pre-series/prototype cars ...
I "dunno"....;
do others here have more insight into this? Hans, Jon, Garry??
Achim
(still without WW tires...; have to solve that problem)