Ian Balfour in Famous Diamonds p. 193 has supplied the answer to my query: The diamond auctioned in 1964 was not one of the diamonds Cardinal Marazin left to Louis XIV.
The logic is very simple. The diamond auctioned in 1964 was an emerald cut of 30.58 carats. Of the diamonds referred to as the Marazin diamonds only the Sancy had a carat weight larger than that. The history of the Sancy, which is now in the Louvre and has remained a pear shape, is well documented.
It would be interesting to know who owned the diamond auctioned in 1964 and to whom Jack Arpels sold it subsequently. I could not find any information on that in Vincent Meylan's book on Van Cleef and Arpels. Has anyone read another history of the firm which might shed some light on this diamond?