Swartchild Black Shield Clock OPEN LOOP Mainspring 4.00 x .33mm x 24"

Swartchild & Co Clock Mainspring, OPEN LOOP End, Dennison 5/32 x .013 x 24, from the 1950's, steel, new in envelope. See images for further details. The stain on the envelope is leftover tape sticky-goo. I specialize in hard to find watch & clock parts and all parts are unconditionally guaranteed. Images do a pretty good job of representing the item