Production of reference 3525 was launched in 1939. Different versions in regard to case material and dial layout, including models signed Oyster Watch Co., are described and illustrated in I Cronografi Rolex - La Leggenda, Pucci Papaleo Editore, pp. 162-192. A similar model with black dial and without outer tachymetre and telemetre scales is described and illustrated on pages 190 & 191.
Gay Frères, located in Geneva, were specialised in manufacturing jewelry but were also renowned for producing high quality bracelets for wristwatches.