HR Mainspring SA406 for Illinois 16s Factory No. 47309 for 60hr - Alloy

HR Mainspring for Illinois 16s, No. 47309 for all 60hr railroad movements (Bunn Special), alloy, new in envelope. See images for precise mainspring specifications. 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.