International Model 333.149. "Maeder-Leschot, Biel, Switzerland" symbol on inside of case, along with "Stainless Steel Back, Bezel Gold Plated 6 40 Microns "M0" and the number 333.149.
Movement marked Swiss with no import stamp or "USA". Case back exterior marked "Bulova Swiss" and "Waterproof"; with the number 1.73683.
This watch is identical to Rev. Rob's with the exception of the markings being slightly different and it lacks the "International" text on the face. After viewing Rob's example and comparing it to mine, as well as reading the previous thread, here are my thoughts. This would appear to be "International Collection" produced entirely overseas for the International (non-US) market. My thought is that if a watch has "International" on the face it was a European design introduced to the US market and a blank face was marketed in Europe and/or Canada. It would seem that 333.149 is the designation of the case/watch (same as Rob's) and 1.73683 is the serial number. The back of this case issuper clean; first character of S/N is absolutely a "1" and not an "I".
That said, I would call this an International "333.149", following the lead of a couple of the previously noted ads that give "International" watches a number designation, as opposed to a name. Thoughts?
Usually the numbers inside these casebacks are reference numbers, but may also include serial numbers.
The reference numbers make it simple for your watchmaker to order parts for the case, and by extension, the movt as well, because the reference number describes the features. (A previous incarnation of this system can be seen with Bulova reference codes) I suspect this watch has a name or maybe even a different number model. As an example, an Omega Speedmaster Professional is the name of the watch, while 3570.50.00 is the reference number that describes the version. Many companies do this, and I suspect Bulova was doing this early on with the International series. Bulova now does this all the time.