Newall Security Mainspring #503 for Waltham 18s Model 1877 No. 2203 - Steel

Newall Security Mainspring #503 for 18s Waltham Model 1877, Factory No, 2203, steel, 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 is hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.