Swartchild Black Shield Mainspring 440761 for Hamilton 12s No. 3328 - Steel

Swartchild & Co Black Shield Mainspring No.440761 for Hamilton 12s movements, Factory No. 3328, steel, new in envelope. See images for further details. 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 suitable job of representing the item.