It is widely believed that Kate received this charm bracelet as a wedding gift from Camilla, Duchess of Cornwall.
It is certainly a bespoke piece, make no mistake about that. The letter “C” is scrolled on one side of the charm, with a crown design imprinted above it (it is her official monogram). This was definitely made just for Catherine.
The bracelet is a yellow gold cable link bracelet. It doesn’t look like there’s a Toggle clasp on this, so I think there is a clasp on it that snaps shut.
According to information from Diana’s Jewels, the other side of the charm has another “C” on it encircled with a perfect round circle. This appears to be Camilla’s monogram.
Kate wore this bracelet a few times. She wore it at Wimbledon in 2011.