Robusta Mainspring No. 1257 for Bulova 10BC, 10BS - Steel

Robusta No. 1257 steel mainspring for Bulova 10BC, 10BS, Unitas 180, 185, AS1200 & Benrus BR caliber movements, plus likely others. See images for precise mainspring specifications. I specialize in hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do an adequate job of representing the item.