Checking the ads we now have, the price lists, and discussions of other examples for Engineer "G" (and info for possible Engineer "H"), I was unable to distinguish between the "G" and "H" variants. While the ad says "yellow or white", the price lists from 1964 show a "G" variant and "H" variant with same $45 price. There has to be some way for Bulova to ship either the Yellow or White version, and this method is unique Bulova model numbers. These model numbers often have different variant letters, but sometimes don't. They may have same prices, or different prices. For the "G" vs "H", the price is the same, the model numbers are unique.
We have some crystal specs for "G" and "H". They take the same crystal, and the crystal package says "Engineer G,H"
We could not determine if others in White or Yellow were "G" or "H", but at that time we only had an ad for the "G", so we voted to ID as "G", noting it is just as likely to be the "H". We decided this conveyed more information about the watch than ID'ing as "Generic Engineer (w/o variant letter)"
Some may say "...but we have an ad showing this watch as G and noting white or yellow". Yes we do. The original source material for the black and white ad may have been in color. Then we would see the one pictured - the "G"- may be yellow. The color info is often lost when published as black and white. This begs the question "why didn't the text of the ad note one color is one letter variant, and the other color is different variant?" 1. If the source ad was in color, that wasn't necessary. 2. The cost associated with adding more text description drives up the price of the black and white ad. When the person wishing to buy the watch comes into the store, the dealer can then give them either White or Yellow...which in subject example, most likely have different variant letters.
I'll check for any new ads or other info for "H" variant. As in other similar examples, I will also vote for tentative "G", realizing that vote could as easily be for "H". The subject watch most closely resembles the ad for "G", and some of us decided its better to ID as "G", noting it could as easily be the "H".