Pennsylvania Mainspring for N.Y. Standard 0s No. 6133 - Steel

"Pennysylvania" Mainspring made by Waltham for N.Y. Standard 0s movements, Factory No. 6133, steel, new in envelope. See image for further details. Why Waltham chose to call these "Pennsylvania" instead of just the typical generic "Unit Resilient Main Spring" they manufactured for use on watches other than their own may forever be a mystery. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a marginally adequate job of representing the item