Elgin Factory Mainspring for 20/0s grade 617 automatic - Alloy

Elgin Factory Mainspring factory for 20/0s grade 617 automatic 17j movements, alloy, new in sealed envelope. See images for further details. These were available in a couple of different strengths and those that I can supply are shown in the drop down list. I likely have several of these in each strength so the one you get may differ 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