MERITAS Mainspring for 12s Trenton M#1 Pocket Watch - Steel

MERITAS Mainspring for 12s Trenton M#1, steel, new in envelope. I do not believe this is the same mainspring for a 12S Ingersoll-Trenton but I could be wrong - my notes show a different type and not a T end like this one has. 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.