Possible 1957 Bulova 23 'O'
Case is 10KT Yellow RGP (as engraved inside) dated to 1957 - L7. It is the same style case as the G, GW, and OW. It is running on a 1956 - L6 10BPAC movement. It has the black sunburst dial with luminous hands and markers.
My reasoning for the 'O' variant designation is based on the ads provided and the 1958 pricelist. In 1955 the variants GW and OW do not exist, they were in the new model section of the 1958 pricelist. In that same 1958 pricelist the variants G and O no longer exist (appear to have been replaced by the *W). I cannot find an ad for an O variant, but based on the 1962 ads stating/showing OW as the matching black dial (w/ luminous) to the G/GW, as well as the 1958 pricelist showing OW as black...O would have been the black dial match to the G, or so my theory goes.
1955 ad for G 1962 ad for GW/OW 1962 ad for OW (courtesy of watchophilia) Here is a current non-variant identical model, possible variant match update to this one, if assigned
The "main" price lists were released quarterly. There were monthly supplements released post quarterly: 2 months updating previous quarterly....then a new quarterly list. So the "main quarterly" were dated at least one month out from pub date...but w/ supplement data, should be pretty current. I believe the dealers/distributors had to have some way to "ask for" a particular watch model/variant to get it in stock to sell. I believe Bulova would not send out or sale a watch for which there was not a unique bulova model number, which would have been required for both sales and used internally for manufacturing. I doubt Bulova put together a model/variant and then later assigned a unique model number. These unique model numbers have more info than we are seeing. There are patterns which I have not discovered. Perhaps patterns like "the second digit of unique model number referrs to gold color/content" etc... I just made that one up, but you get the idea. They didn't use a random charactor generator to assign these numbers. They mean something for production, sales and record-keeping. I just can't go fishing for the patterns (yet)