At the center of this collaboration is the base movement of the watch, the Caliber 135, which was produced by Zenith from 1949 until 1962. The original mechanism was created in two distinct versions– one intended for commercial use and the other specifically for taking part in chronometry competitions. The latter, known as the Caliber 135-O, excelled in its category, holding the most awards of any competitor for five consecutive years. As such, the Caliber 135-O certainly fulfilled its original purpose, but nearly 70 years later, Zenith saw an opportunity to revamp the Caliber 135-O into something almost entirely different.