As reported by The History Blog:
Conservators have discovered a four-inch gold hairpin that once belonged to Catherine de Medici, wife of King Henry II and Queen of France from 1547 until his death in 1559, in a communal latrine at Fontainebleau Palace. Archaeologists were excavating the Henry IV courtyard at the royal palace outside of Paris in preparation for an upcoming restoration project when they found the precious object.
The pin is identifiable as Catherine’s because it is decorated with a pair of interlocking C’s that look exactly like the Chanel logo but are actually her monogram from when she was Dauphine of France, i.e., married to the heir presumptive, between 1536 and 1547. When Fontainebleau Palace conservator Vincent Droguet cleaned the encrusted grime off the jewel, he noticed the remnants of a white and green finish in the monogram area. White and green were Catherine’s colors...
How it got there is and will doubtless remain a mystery. She had a royal commode of her own and it’s highly unlikely she would have used a communal latrine even under the direst of excretory pressure. Droguet surmises that the pin was either stolen by or given away to someone who then lost it or dropped it in the toilet.