Just like the majority of watchmakers in the 1970's, Rolex was experimenting with quartz movements from regular battery driven to LED displays. In 1971, in conjunction with the other major Swiss famous reference 5100 made in a limited edition in white and yellow gold. Rolex ultimately wanted to develop their own caliber (similar to what they did on the Rolex Daytona) and eventually in 1977 launched their own quartz caliber which would be fitted to the Oysterquartz Datejust and Day-Date models. Their movements were finished in the highest quality available at the time and one only needs one look to see that it is unlike almost any other quartz. It makes complete sense that in this time of testing, a quartz movement that featured a perpetual calendar would be an attractive feature to potential clients. According to some scholars it appears only about eleven examples were produced but as most trial and prototype pieces they were often destroyed so watches like this example are extremely rare. It is interesting to note as well that instead of the serial number of the watch, it is stamped with what is most likely to be prototype testing numbers ( in this case 790 and 799).