re: #40 Blind Frog Belly White

Gold filled means two sheets of gold sandwiching ‘base metal’, usually brass. They came in various thicknesses of gold, with 25 year being about the thickest. At that time, watch companies like Elgin, Hamilton, Waltham etc. sold movements only, and other companies sold cases. Jewelers selling watches to consumers would pair the movement with the case according to the customers wishes.

So, you might find a solid gold case with a 7j movement, because the buyer cared more about the case. And railroaders had to have high-grade movements (like the 21j Hamilton I showed), but might put it in a nickel case.

Because the accuracy of the movement was more important. Makes sense. So 15 jewels would be neither best or worst - probably a pretty decent medium. It’s always kept good time for me since the last cleaning.