Favorite Rational Mainspring 511M for Font 10, 16, 22 & Aurore 18 - Steel

Favorite Rational mainspring No 511M for Font caliber 10, 16, 22 & Aurore caliber 18 movements plus perhaps similar ébauche watches as well, steel, new in envelope. See images for further data and precise mainspring specifications. I specialize in hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.