With Patek Philippe Extract from the Archives confirming production of the present watch in 1956 and its subsequent sale on 26 February 1957.
Reference 2540 was in production between 1954 and 1960 and was Patek Philippe's first square wristwatch fitted with an automatic movement. The model was also available with mechanical movements calibre 12'''400, ref. 2540/1, and calibre 27 SC with sweep centre seconds, ref. 2540/2.