Here is a really curious one in an engraved Bulova case with a "Star" next to "Waterproof" on the back. The only date code observed is on the case back interior - "M1". Full luminous black dial and stainless case. I bid on this one from fairly bad photos, not able to do detrmine if the case was engraved, sanded or badly scratched. To my great satisfaction, it's factory engraved on the top surface as well as the sides. I installed the band, it's not original equipment.
I find this case shape in the linebooks from 1961 to 1964. In 1961-1963 it's a Bulova 23. In 1964 it becomes a Regatta 23. Each listing gives 3 variants. One of the 3 is full number luminous black dial, which this one is. All of the linebook photos appear to show the same watch photo (white dial variant) on the same band, except 1962 that shows the black dial in a smooth case with leather.. The model number changes every year as does the variant letter.
I suspect this is a 23 ZAW which would be the very first black full luminous dial in this casing that became the smooth case 23 YW in 1962 on leather, the 23 YY back on an expansion band with smooth case in 1963 and finally the Regatta 23 NN in smooth case with expansiion band in 1964. Whew!
Looks to be a one year watch.
1961 Bulova 23 "ZAW"
Watch face has excellent glow and appears original. I think this one spent the majority of the last 60 years in a dresser drawer. Keeps excellent time as well.