Rolex - An 18ct gold diamond and sapphire set cocktail watch

circa 1926, the unsigned square silvered guilloché sunburst dial, 12mm wide, with black Arabic numerals, blued moon hands and chemin de fer chapter ring, signed but unnumbered 15 jewel 'Prima' mechanical crown wind movement with liveried crown, case, 15mm wide, front set at 12 and 6 o'clock with a shield shaped facetted sapphire and six single cut diamonds, articulated lug covers each set with a further 12 single cut diamonds, case side with decorative engraving, verso hinged at 12 o'clock, plain and polished, inner signed and numbered 36489 111 together with Glasgow import marks for 18ct gold, to an aftermarket black leather cord strap with steel buckle