NuVigor Mainspring No. 21½ for Gruen 300, 350, 530, 531 - Steel

NuVigor No. 21½ steel mainspring for Gruen caliber 300, 350, 530, 531 movements, and quite likely others. steel, new in envelope. 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 a pretty good job of representing the item.