of all the standard production watches is the 5261R Aquanaut annual calendar. While denominated as a ladies watch (which makes no sense to me) it comes in at 39.9 mm, which less than 1 mm smaller than 5164R. The 5261R is one mm larger than the 4947/1A which has the same complication as the Aquanaut and is NOT described as a ladies’ watch, rather “suits all wrists”. While I don’t know if In the metal the dial color of the Aquanaut will be very attractive or not, certainly I would not feel at all hesitant to wear this “ladies” watch because of its classification.. Best, Patekova