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

BOREL Mainspring SA406 for Illinois 16s 60hr RR movements, Factory No. 47309, 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.