WATCH-CRAFT Mainspring 3849W for Felsa 21N, 23, 23N, 24, 24N, 25, 25N, 81, Elgin 842 - Alloy

WATCH-CRAFT Mainspring 3849W for Felsa 21N, 23, 23N, 24, 24N, 25, 25N, 81, Elgin 842 caliber movements plus perhaps similar ébauche movements, white alloy, new in envelope. See images for precise mainspring specifications. The F21 & F81 were base calibers for many Swiss watches, such as Dugena 563, Glycine 30. 
Juvenia 815, Winton, 6, 441-17.  I likely have several of these so the one you get may differ slightly from the images. I specialize in hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.