The original was a gift to Marie Caroline Gibert de Lametz, who was a French stage actress, from her husband Prince Florestan I. Florestan ascended to the throne in Monaco in 1841, but he was never prepared to assume the role of prince. He had been an actor in the Théâtre de l'Ambigu‑Comique — and the real power during his reign lay in the hands of his wife. The two were considered a very compatible couple as their background in the legitimate theater brought them together. The necklace had already been in the Grimaldi family for some time, and its origin unknown.
The necklace was originally a watch and along with the case was made in Paris in 1848. The watch mechanism was removed probably for repair but never returned to its case. In the early 1900's, during the reign of Louis II, the interior of the locket was re-configured to hold photographs of loved ones, which had become very popular with the wealthy. When given to Grace, the locket was empty of previous photographs. Grace eventually had one photograph of Prince Rainier in one section, and a photo of both children taken that year (1959) in the other section. In 1965 after the birth of Stephanie, a photo of the three children was now opposite the original photo of Rainier she had placed there some years earlier.
The Miniature Painting on the original watch was Painted by Samuel Henry Alken -- c1841.