HR Mainspring A230 for Hamilton 20/0 & 21/0s No. 2921 - Steel

HR Mainspring A230 for Hamilton 20/0s & 21/0 movements, Factory No. 2921, steel, new in envelope. See image for precise mainspring specifications. 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.