HR Mainspring SA508 for 12s NY Standard Factory No. 4284 - Alloy

HR Mainspring SA508 for NY Standard 12s Movements, Factory No. 4284, Tongue-end, alloy, new in envelope. See images for precise mainspring specifications. Yes, I know some of the the envelopes says 8284 but that's a misprint. 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.