Rolex launched the reference 3525 in 1939 coinciding with the outbreak of the Second World War and production ceased shortly after the end of the war. Available in pink gold, yellow gold, two-tone or stainless steel, it marked a milestone for Rolex as it was the first chronograph fitted in a waterproof Oyster case. The 3525 can be divided in two main series, with the first one (1939-1942) having the reference and case number engraved on the outside case back, and the second one (1942-1946) having the reference number on the inside case back and the case number engraved between the lugs. The present lot belongs to the first series and presents an early serial number for the reference. Referred to as 'Monoblocco' by collectors, the upper case including bezel and lugs is made from one piece only.

The 3525 gained even more popularity as it was one of the models that Rolex sent to British military men held in German imprisonment camps during the war. In this bold scheme, Rolex offered their watches instantly and would accept payment whenever possible later on. Some British officers ordering Rolex watches this way later became known for taking part in a mass escape from the German prison camp Stalag Luft III in 1944. This event served as inspiration for the 1963 film 'The Great Escape', starring Steve McQueen.