Alloy Mainspring for Buren 40, Gruen 210, 212, 301, MST 281

Unmarked Maker Swiss Mainspring for Buren caliber 40, Gruen caliber 210, 212, 301 & MST caliber 281 movements plus perhaps similar ébauche watches, white alloy, new in tiny envelope. See images for precise mainspring specifications.  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 an adequate job of representing the item.