Swartchild Black Shield Mainspring #4395A for 18s N.Y. Standard 2190 - Steel

Swartchild & Co. Black Shield Mainspring #4395A for 18s N.Y. Standard movements, Factory No. 2190, steel, new in frail or chopped envelope. Sometimes the envelopes are big, sometimes they are small and sometimes they barely say anything at all. See images for further details. I likely have several of these so the on 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 barely adequate job of representing the item.