Marco Mainspring #732 for NY Standard 12s Model K No. 4284 - Steel

Marco Mainspring No. 732 for NY Standard 12s Model K movements, Factory #4284, steel, new in envelope (some of the envelopes are mis-marked 4248). See images for further details. 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.