The Jonker was a South African diamond discovered in 1934. Its considerable size—an eye-popping 726 carats—made it, at the time, the world’s largest uncut diamond. Winston negotiated with De Beers on the purchase of the rock, which went on an extended display tour across the U.S. once it arrived here. In 1936, after painstaking calculations, the diamond was cut into twelve gleaming gems.