This is my Elgin Grade 96 from 1895. It is size 18, 7 jewels, pendant wind, lever set. The case just says it's "silveroid." According to a forum post on the internet, silveroid is a copper-nickel alloy.
Initially it would run for a minute or so and stop. Currently it seems to be running continuously. I'll carry it for a day or two and see. Sometimes these just need some jostling to get them going and stay going.
Acquired: 2019
Circa: 1895
Current condition: Doesn't stay running for long