Vertex, a diamond cocktail watch

Vertex, a diamond cocktail watch, 1920s and later, the circular white enamelled dial with blued steel hands, the case and front of bracelet of concentric design, millegrain-set with circular- and single-cut diamonds, to a later bracelet, manual winding movement signed Vertex, case back interior marked platinum, numbered 699/4587, dial 1.2cm diameter, bracelet length 16.5cm