From reading the thread where the Spencer was discussed, it seems to me that the conclusion was Duo Wind would be the model if the watch states "Duo Wind" on the dial and pre-dates the appearance of the Spencer circa 1952 (at which point, the "Duo Wind" went away and "Self-Winding" appeared on the dial).
Is that a correct interpretation of that prior discussion? (If so, this one would be a Duo Wind.)
'DUO WIND' had a bi-directional winding mechanism (1950 -51) and will state so on the Dial. The 'DUO WIND' insignia disappears from Bulova Dials around 1952 as the uni-directional auto's came into play and the Watches take on their own individual Names...from what I can gather.
The automatic movements used in Bulova watches are all bi-directional rotating/charging, and the Duo in Duo Wind probably refers to the ability to wind the watches by hand as well as automatically. The change from Duo Wind to Self Winding is probably just an update to the wording on the dial, as we see 1952 ads for Duo Wind watches with "SELF WINDING" on the dial.
This is just my opinion, of course.
The Bi-directional winding automatic system was new at the time, having been unidirectional first. This was spearheaded by Felsa, with their "Bidynator". Other Bidirectional movts were used, like the A. Schild. (can't remember the cal)
The Duo Wind, I believe, refers to the bidirectional winding, since all the models could also be wound by hand and was nothing new. I can't say for certain, but I'm pretty sure Bulova used its share of uni winding movts also. These especially would have been the US Bulova designed ones, like the 11AFAC. I'm having trouble locating the specs, but will update this when I do. The micro autos were certainly all uni.