Swartchild Black Shield Mainspring #B4391 for 16s Trenton No. 344 - Steel

Swartchild Black Shield Mainspring #B4391 for 16s Trenton Pocket Watches, Factory No. 344, steel, new in frail envelope. Could also very well fit in other watches as well. 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.