Swartchild Black Shield Mainspring #4333 for Waltham 12s movements No. 2224 - Steel

Swartchild Black Shield Mainspring No. 4333 for 12s Waltham Factory No. 2224, hook end (see images), steel, new in frail envelope. See images for further details. Notice the hand scribed "Black Shield" on the spring. 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 and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.