Beacon Mainspring for Longines caliber 10L movements - steel

Beacon mainspring for Longines caliber 10L caliber movements, and quite likely others, steel, 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 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.