Thanks
I am glad you are finding it helpful.
In addition to the two websites above, you will find a great Red Sub sticky thread at the top of the vintage Rolex discussion, and there is a fantastic review of the white dials of the 1680 in the Vrf classics section by Marcello Pisani.
Finally there is are two Gmt threads here on TRF. One in the Rolex reference library and the other by Springer here on this sub forum.