Howard 16s Mainspring Factory No. 2323 (328) - Steel

Howard Mainspring for 16s, Factory No. 2323, most (but not all) are marked with the maker CYY on the actual spring, see images for further details. Evidently the CYY P/N was 74 and while the Old Factory No is 2323, which is largely equivalent to a 328 which measures between 2.75 and 2.80mm, depending on your reference guide. It's worth noting that the Swartchild Guides do show the 328 as a Dennison 20 while others usually show it as Dennison 19 (see last image). I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do an adequate but perhaps somewhat incomplete job of representing the item.