Newall Security Mainspring #428 for 10s Elgin Grade 542, 542 & 546, No. 5726 - Steel

Newall Security Mainspring #428 for 10s Elgin movements, Factory No. 5726, steel, new in envelope. See images for precise mainspring specifications. These are made for grade 542, 543 & 546 (and perhaps others) 10s pocket watches. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do an adequate job of representing the item.