HR Mainspring No. 631 for MST caliber 369 - Steel

HR Mainspring No. 631 for MST (Meyer & Studeli) caliber 369 movements plus perhaps other ones as well, steel, new in frail envelope. See images for further data and precise mainspring specifications. 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.