Swartchild Black Shield Mainspring for 12s Rockford No. 932 - Steel

Swartchild & Co. Black Shield Mainspring No. 4387A for 12s Rockford movements, Factory No. 932, steel, new in envelope. See images for further details. 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.