The 30 jewel Patek Philippe automatic movement, calibre 12'''-600AT, was one of the first automatic movements ever produced by the firm. Over the course of a seven-year period, from 1953-1960, only 7000 examples were produced for different reference numbers - perhaps the most well known of these was the Ref. 2526.
The present model, reference 3403, is perhaps the rarest of the references to feature this movement. It is the only calatrava-shaped watch to feautre this highly jewelled movement. Such models rarely appear at auction.