Helm watches from the 1940s in gold are illustrated on pages 191 and 209 in Le Temps du Cartier by Barracca, Negretti and Nencini; this platinum watch seems to have been a custom-made piece for a special client, much as the Tank watch pictured on page 207 (ibid) was made in platinum as a special order for the Prince of Nepal. Although jewelry and watches made in platinum from the 1910s and 1920s are not uncommon, platinum accessories made just after 1929 and during the war years of the '40s are exceedingly rare. Due to the world's economic and political turmoil of those decades, the availability of certain raw materials such as platinum was severely limited. As a result, platinum would have been prohibitively expensive except for the most stupendously wealthy of Cartier's clientele.