Cas-Ker Mainspring JA120 for 5/0s & 6/0s Elgin Factory No. 2890 / 6098 - Alloy

Cas-Ker Mainspring JA-120 for 5/0s & 6/0s Elgin, Factory No.Factory No. 2890 / 6098, probably made by Bestfit, new in package. See images for further details. 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.