Marco Mainspring #4163 for 19 ligne (19N & 19NN) Omega Pocket Watch - Steel

Marco Mainspring No. 4163 for Omega 19 ligne (19N & 19NN) Pocket Watch, DB&H end, steel, new in envelope. See image for precise mainspring specifications. I know the envelope says 17 & 19 ligne but I'm not sure what caliber they are referring to in 17 ligne. 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.