Talk about coming with a backstory. The wristwatch believed to announce the time of death of President John F. Kennedy is up for sale. The 18-carat Patek Philippe was worn by Dr. Kemp Clark, the doctor who called Kennedy’s death at a Dallas hospital on Nov. 22, 1963. “The family and historians agree on these facts: The watch was on his wrist that day and he called time of death and signed the death certificate,” said John Reardon, Christie’s international co-head of watches. Clark, whose mother purchased the watch for him while on a trip to Switzerland, died in 2007. A portion of the proceeds from the sale will be donated to the Red Cross.