Gruen Steel Mainspring for 12s Guild / SemiThin Movements

Gruen Mainspring for 12s (17 ligne) calibers 730, 740, 754, 756, 758, Guild / SemiThin Pocket Watch movements, and perhaps others too, steel, new in envelope. The envelope specs these as 7½ x 4 but I checked them on my Vigor caliper and they are closer to 8 x 4. I specialize is 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.