Omega Speedmaster Mark 4.5 Professional

The Mark 4.5 is where the Speedmaster gets technical. Introduced in the mid-1970s and produced for only a short window, the ref. 176.0012 Speedmaster Mark 4.5 represents one of the more interesting detours in the Mark series, Omega’s ongoing effort to rethink its most famous chronograph for a new decade. If the Moonwatch is purity, the Mark 4.5 is progression. The 42mm stainless steel tonneau case, with hooded lugs and sweeping radial brushing, continues the muscular design language first explored with the Mark II. Cushion-shaped, solid, architectural. But beneath the 'hesalite' (Omega’s trade name for a type of acrylic crystal), the Mark 4.5 moves in a slightly different direction. The dial adopts the distinctive “TV-style” layout, squaring off the registers and tightening the visual balance while preserving the bold legibility Speedmasters are known for. Powering it is Omega’s automatic Caliber 1045, derived from Lemania’s celebrated chronograph architecture. A central chronograph seconds hand is paired with the highly practical central chronograph minute counter, turning elapsed timing into something instantly readable. Add a day-date display and the result is a chronograph that feels decisively modern for its era. Automatic, 48-hour reserve, 30m water resistance, solid caseback, steel bracelet—this was a Speedmaster designed for the realities of the 1970s: daily wear, real utility, unmistakable presence. Within the Mark lineage, the Mark 4.5 represents the Speedmaster at its most experimental. A moment when Omega was comfortable pushing its icon into new territory. Same mission. Entirely different machine. A Speedmaster for collectors who enjoy the deeper cuts.