Benrus Factory Mainspring for caliber BM - Alloy

Benrus Factory Mainspring for caliber BM movement, alloy, new in envelope. I likely have several of these so the one you get may differ slightly from the images. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. If you need a part for a vintage watch I likely have it so feel free to inquire. Images do a pretty good job of representing the item.