Swartchild Black Shield Clock Mainspring 4.4 x .20 mm x 23¼" Ref 44-20 C59

Swartchild & Co Black Shield Clock Mainspring, Tongue End, Ref. 44 - 20 C 59, from the 1950's, steel, made in France. See image for precise mainspring characteristics. I specialize is hard to find watch & clock parts and all parts are unconditionally guaranteed. Images do a pretty good job of representing the item