Trufit Mainspring for Gruen caliber 290, 291 - Steel

Trufit Mainspring for Gruen caliber 290, 291 movements, steel, new in envelope. B&C Trufit mainsprings were distributed by Barton & Chase of Philadelphia but as you can see they were made in Switzerland. See image for precise characteristics. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.