Watch Model: Elgin National Watch Company (619485?)

Movement Serial Number: Elgin National Watch Company 8739946

Mass: 58.3g

Case Outer diameter: 42.0mm

Crystal diameter:

Thickness: 11.7mm

Movement Dimensions:

https://pocketwatchdatabase.com/search/result/elgin/8739946 

Mainspring

Width: 1.85mm

Length: ~450mm (~18 inches)

Thickness: 0.18mm

Apparently it’s Elgin #824.