Comsco Mainspring #1090C for Elgin 21/0s Factory No. 5724 - Steel

Comsco Mainspring #1090C for Elgin 21/0s Movements, Factory No. 5724, steel, new in envelope. Distributed by Burton M. Reid and Sons. See image for specifications and further details. 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.