Gruen Factory Mainspring for caliber 290 - steel

Gruen Factory mainspring for caliber 290 and quite likely others, steel, new in open envelope. I likely have several of the so the one you get may differ slightly from the images but they are all the same mainspring. 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 a pretty good job of representing the item.