With Patek Philippe Extract from the Archives confirming production of the present watch in 1895 and its subsequent sale on April 8, 1900. The extract further confirms the inner calotte, or inner protection case and also that the watch left the factory with dark blue enamel, a star in rose cut diamonds; engraved case back and bezel.
Pair cased watches manufactured by Patek Philippe are exceedlingly rare and according to reseach only 30 such examples are known. They usually bear miniature enamel decorative mythological scenes with outer chased cases. Pair cased watches such as the present example with decorative enamel and diamonds are extremly rare.
Pair-case watches are illustrated in Patek Philippe Pocket Watches by M. Huber & A. Banbery, 1982, pages 126 and 128