(IDEX Online) - Rihanna wore a $700,000 Jacob & Co diamond watch on a neck choker in June.Now she's come up with another improbable place for a timepiece. Her ankle. The Barbadian singer, 35, wore a customized Jacob & Co watch on a three-strand bracelet with 155 round and emerald-cut diamonds (total carat weight over 70 carats) to the Las Vegas Grand Prix. It is valued at $400,000.She wore the neck watch to Pharrell William's Louis Vuitton debut fashion show in Paris in June.The white gold Jacob & Co Brilliant Flying Tourbillon was set with 338 baguette white diamonds and one cabochon-cut diamond, total weight over 30 carats.Pic (left) courtesy Jacob & Co's Instagram page and (right) Rihanna with neck watch