During the 1970’s, when many watch manufactures were understandably concerned about the threat that quartz accuracy posed to their mechanical watch businesses, some of them developed hi-beat movements in efforts to push the boundaries of mechanical movement accuracy. Some of those high-beat movements were developed in-house, while other manufactures, including Ulysse Nardin, used ETA movements as a base.

https://forum.tz-uk.com/showthread.php?143679-Ulysse-Nardin-36000-info-and-pics

AND Zenith…