Rolex Datejust 31 31 mm 278240BKRO Steel Black

The Rolex Datejust is one of the most recognized and enduring watch designs in horological history, having introduced the self-changing date complication to the wristwatch when it debuted in 1945. Over the decades, the Datejust has evolved through countless dial configurations, case sizes, and material combinations while retaining the essential proportions and design language that made it iconic. The 31 mm mid-size case positions this reference perfectly between the classic 28 mm ladies' Datejust and the full-size 36 mm, making it a favorite among wearers who appreciate a refined, wrist-flattering footprint without sacrificing legibility or presence.

Reference 278240BKRO is built on Rolex's robust Oyster case in polished and brushed stainless steel, measuring 31 mm across — a diameter that sits elegantly on a wide range of wrist sizes. The case is sealed by a screw-down Oyster crown, giving the watch a water resistance of 100 meters (330 feet), so it transitions effortlessly from formal occasions to everyday activity. The stainless steel domed bezel frames the dial with understated architecture, its smooth arc recalling the earliest Datejust references and lending the watch a timeless, unadorned sophistication.

The centerpiece of this reference is its bright black dial dressed with Roman numeral hour markers. Roman numerals have long been associated with formal watchmaking and classical clockmaking traditions, and on this black ground they create a high-contrast, immediately legible display that feels simultaneously vintage-inspired and thoroughly contemporary. The overall aesthetic rewards close inspection while reading effortlessly at a glance — precisely what a daily-wear dress watch should do.

Power comes from a Rolex automatic movement, the technology that has defined the Datejust since its inception. Automatic winding through an oscillating rotor means the watch winds itself during normal wear, requiring no manual intervention as long as it is worn regularly. Rolex automatic movements are celebrated across the industry for their reliability, precision, and longevity, and they are serviced through Rolex's global network — an important practical consideration for any serious collector or daily wearer.

The watch is completed by the Oyster bracelet, Rolex's original and most versatile integrated bracelet design. Its three-piece link construction in stainless steel is both robust and refined, lying flat on the wrist and complementing the polished surfaces of the case beautifully. The Oyster bracelet has proven itself over decades as one of the most comfortable and durable metal bracelets in watchmaking, an engineering achievement as much as a design one.

At Bizak & Co., we specialize in sourcing and presenting references like the Datejust 31 278240BKRO to discerning buyers who understand quality and value. Whether you are purchasing your first Rolex or adding to an established collection, this reference offers the ideal intersection of heritage design, practical performance, and understated luxury. Visit bizakandco.com or contact our team directly to ask about this reference, confirm current availability, and buy online with confidence from a trusted luxury watch dealer.