There was no officially-offered Rolex stainless steel/gold 1680 Submariner. Two-tone submariners did not enter the Rolex product line until the sapphire quick-set Subs of the 1980s. What most likely occurred was that the selling dealer "customized" the standard steel 1680 model per customer's request. This is not hard to do, after all, even using all authentic Rolex components. The only parts that will need to be changed with pieces from the gold model (1680/8) are as follows:
1. Bezel and insert;
2. Dial, hands and datewheel;
3. Crown; and
4. Swap standard all-steel Oyster band with two-tone Oyster band from 1675/3 GMT Master.