Elgin Factory Mainspring for AS caliber 1187 - Alloy

Elgin  Factory Mainspring No. 6711, for AS caliber 1187 and probably a very obscure Elgin grade somewhere, (tongue) end, alloy, new in envelope. I haven't yet found an Elgin grade that's based on this movement. See images for precise specifications. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a satisfactory job of representing the item