BESTFIT Mainspring 312A for Gruen 139, M. Favre 139, MST 284 - Alloy

BESTFIT Mainspring 312B for Gruen 139, Marc Favre 139, MST 284 caliber movements plus perhaps similar ébauche watches, white alloy, new in envelope. See images for precise mainspring specifications. I likely have several of these so the one you get may differ slightly from the images. I specialize is hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a satisfactory job of representing the item.