The watch was appraised in 1989 by a member of the National Association of Jewelry Appraisers. I have included a .pdf copy of this 1989 appraisal and description.
1.4 diameter X .1 thick
Cartier - A Rare Victorian Gold Sovereign Coin Watch, circa 1930
the coin dated 1895, opening to reveal a hidden watch, the circular cream dial with Roman numerals and blued steel hands within an engine turned surround, signed Cartier, (originally with fitted case by Cartier London.)
The watch was appraised in 1989 by a member of the National Association of Jewelry Appraisers.
Cf: Le Temps de Cartier, Fondation Cartier pour l'art contemporain, 1989, p. 29 for an illustration of a similar watch face, p. 1444-145 for examples of other pocket watches fitted in coins.