According to our research the present watch is a very rare example of the platinum limited edition launched by Cartier in 1981.
Timepieces belongings to such series in the 1980s are recognizable by the colour of the numerals, a beautiful deep burgundy.
These platinum special series are extremely rare. In 1979, several models like the Santos-Dumont, the Ellipse and the Baignoire were part of a special series in platinum with burgundy numerals specially made for Cartier Paris. This special series is illustrated in Cartier Le joaillier du Platine by Franco Cologni and Eric Nussbaum, pp. 226-227.