Swartchild Black Shield Mainspring #4341½ for Waltham 0s & 3/0s No. 2230 - Steel

Swartchild Black Shield Mainspring #4341½ for Waltham 0s & 3/0s model 1907 movements, Factory No. 2230, steel, new in envelope. See image for further details. 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 and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.