I think there's one more newspaper/newer ad showing diamond dial 23's. The Bulova model price lists have lots of information about diamond dial, gold color/content, dial color, jewel count, and various configurations of dial/case/jewel count- AND assign model names to these combination of characteristics. We just have to be able to interpret these lists. One method is by cross-referencing these characteristics to models for which we have ads showing said characteristics.
Using the Bulova 23 "ZW" above as an example. The ad doesn't state gold content/color, but the model list does. Relative prices infer gold content- as cross-referenced to existing ads on site.
Below is a page of the Fall 1958 Bulova model price list. Under one section of these lists it subsets "Men's Diamond" models. We see both Bulova 23's and Beau's w/ diamond dials, but we also see the gold color of the Bulova 23 ZW above listed as White (W). I have cross-referenced many of these list entries w/ a (Y) or a (W) in the name to ads we have on site, and in most instances, the ads which state gold color indicate the list entries w/ (W) correspond to availability in white gold. Some ads state various gold colors, but most include (W) white for list entries containing the (W) in the first column, and none suggest they were not "also available in white gold". A way to validate my interpretation of the lists.
