Rolex Datejust 31mm Dark Grey Oyster 278240Overview The Rolex Datejust was first released in 1945 and a very important part of the Rolex collection. The reference 278240 is the current Datejust in 31mm. Introduced in 2020, it is the latest reference for the Datejust 31. New improvements include a new movement with an improved power reserve of 55 hours and some new dial colors. Specifications Brand : Rolex Model Name : Datejust 31mm Reference : 278240 Material Steel Movement : Rolex Calibre