Omega Seamaster 300 Prototype

About this reference

The Omega Seamaster 300 Prototype 87233956 is an experimental stainless steel diver produced in the late 1960s, specifically around 1968. Collectors prioritize this reference due to its unique case construction, which features a massive, asymmetrical "bullhead" or "helmet" design intended to test ergonomic crown placements and enhanced water resistance. It houses the manual-wind Calibre 861 movement, the same caliber utilized in the Speedmaster Professional of that era. The dial typically features a matte black finish with oversized luminous markers and a distinctive orange central chronograph hand. Because these were internal prototypes and never reached mass production, they are exceptionally rare, with only a few known examples in private hands. On the secondary market, these prototypes occupy a high-value bracket, typically transacting in the mid-to-high five-figure range. A notable example sold at a 2018 Phillips auction for approximately 50,000 CHF.