Jurgensen Mainspring #658A for 12s Hamilton Watch No. 6021 - Steel

Jurgensen Mainspring #658A for 12s Hamilton Movements, Factory No. 6021, steel, new in envelope. Could also fit in other watches as well. See images for precise specifications. 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.