Marco Mainspring #411 for Hamilton No. 318 - Steel

Marco Mainspring No. 411 for Hamilton 16s movements, Factory No. 318, steel, new in envelope. The package says grades 974 and 975, which is accurate but incomplete as this mainspring will work in other 16s grades as well.  See images 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.