Omega, chronograph, Cal. 33.3CHRO powered, water-resistant, stainless steel, step-design bezel, black dial, 38 mm in diameter dial size, circa 1940s. This is one of the rare water-resistant chronograph among the 33.3 chronographs that have been popular in recent years. The 38mm step design screw back water-resistant case with a big crown and a massive structure is overwhelmingly attractive. The dial is in two-tone black and gray with a tachymeter (green) and a decimal scale (white), a unique and rare dial design with a color scheme and layout unique to Omega of this era. It is highly regarded for its coloring, intricate dial design, and oversized case of over 38mm, which is not seen in other famous brands of the same era such as Patek Philippe, Rolex, Longines, and Universal.