According to Louis Cottier’s records only two examples of this watch in such a small size were made for Patek Philippe; three others were made for Wittnauer in 1940. A similar watch is published in "Patek Philippe Wrist-watches" by Martin Huber and Alan Banbery 1998 p. 244. The "World Time" system was invented by Louis Cottier and employed by Patek Philippe Vacheron & Constantin Agassiz and Rolex.