Royalty Philadelphia, USA. 10th January 1956. Prince Rainier of Monaco and film actress Grace Kelly show off the engagement ring to her mother at the home of Miss.Kelly's parents a few days after their announcement. [Getty Images]

Royalty, Philadelphia, USA, 10th January 1956, Prince Rainier of Monaco and film actress Grace Kelly show off the engagement ring to her mother at the home of Miss,Kelly's parents a few days after their announcement (Photo by Paul Popper/Popperfoto via Getty Images/Getty Images) — see more

Royalty, Philadelphia, USA, 10th January 1956, Prince Rainier of Monaco and film actress Grace Kelly show off the engagement ring to her mother at the home of Miss,Kelly's parents a few days after their announcement (Photo by Paul Popper/Popperfoto via Getty Images/Getty Images)