Newall Security Mainspring #1916 for Kurth 300 thru 314 + 400 thru 404 - Steel

Newall Security Mainspring #1916 Kurth calibers 300, 301, 304, 310, 311, 314, 400, 401, 404 & 410 plus perhaps similar ébauche watches, steel. See image for precise characteristics. 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.