What brand did Sir Malcolm Campbell endorse in 1933?

Sir Malcolm Campbell endorsed Rolex in 1933 when he sent a telegram stating that the Rolex watch he wore during a driving record attempt performed splendidly despite rough usage. This endorsement led Rolex to feature the telegram in their advertisements, highlighting one of their first major sports endorsements. The advertisement showcased Sir Malcolm Campbell's experience, emphasizing the reliability and durability of the watch during high-pressure situations.