Just stumbled upon this old thread .... great topic for serious collectors
When you mentioned 6 different dials up to year 1960, do you actually mean GMT 6542 ? Because 1675 came out only in 1959.
In any case, I don't think there are many in this forum who would even be aware of these differences, and even if there are, can't be bothered to debate or comment much.
Still, the 1675 is my
absolute fav watch both as a collectible as well as a daily beater.