Wyler Genuine Mainspring for Buren caliber 690, 691, Elgin Grade 677 - Alloy

Wyler Genuine Material Mainspring for Buren caliber 690, 691 movements, alloy, new in envelope. Mainspring is aiso suitable for Elgin Grade 677 movements as they were Buren based.  The Buren 690 was found in many other pocket watches, and since Wyler had a couple I could see them there. See images for precise mainspring specification. While it says Genuine Wyler Material, Wyler didn't really make anything - they sourced movements & parts from various Swiss makers (such as Buren), but they did package their parts to sell to fix those movements. 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 an adequate job of representing the item.