Cartier, a rare twenty dollar coin watch

Cartier, a rare twenty dollar coin watch, C1950, mechanical jewelled lever movement, silvered dial, black Roman numerals, outer five minute division, circular case, back secured by two screws in the band, hinged within a United States of America Twenty Dollar coin, the front with Lady of Liberty dated 1906, the reverse with the bald eagle, the watch revealed with the thumbpiece in the milled band is pressed, dial signed, diameter 34mm