The Longines Ultra-Chron series is important because it was the significant watchbrands mechanical (automatic) response to electronic watches and quartz (1969 following), especially. The hi-beating caliber was quite a success and sold numerous times but it came in different grades: there was a standard Ultra-Chron, highly precise and reliable. And there was the Chronometer-grade Ultra-Chron -- finely adjusted to meet even higher and highest standards. As these were priced between 25 and 40% higher than the standard Ultra-Chron depending on the exact model, they sold much less and as they were quite often cased in solid gold cases, many of these few made and sold, were smelted in the last 5 decades, unfortunately -- making the left pieces important and relevant collectibles.