Kate Middleton, 38, and Prince William, 39, have been married for nearly 10 years, since April 2011. Before they tied the knot, the couple dated for around eight years.
The ring worn may have a personal and sentimental meaning, according to CEO of Le Vian Eddie LeVian.
He told Express.co.uk: “This beautiful, delicate ring is understated in style, but the very personal message hidden within it from a future King makes it an enormously romantic royal jewel.
“William gifted Kate this Victorian rose gold band encrusted with pearls and garnets while they were still at St Andrews University where they met as students.
“It’s no surprise Kate was seen wearing it at her graduation.
“It was a milestone marking her own achievements but also a day which put her on the threshold of a new chapter in her life together with William beyond university.”
While in the Royal Family, Kate has worn various eye-catching and sentimental pieces of jewellery.
She was famously given the sapphire and diamond engagement ring which once belonged to Princess Diana.
Prince William also gifted his wife with a diamond eternity ring following the birth of their first child, Prince George, seven.
However, the jewel given to her at university may have been one of the first personal pieces she received from her husband.
The simple band features a row of gems which have a significant meaning to the couple.
Eddie continued: “The ring is adorned with both Kate and William’s birthstones, in a celebration of their bond and the beginning of their intertwined destiny.
“Pearls are a June birthstone – William was born in June – and they symbolise love, purity, humility and innocence.
“Garnets are the birthstone for January, when Kate was born, and were named by the ancient Greeks for their colour resembling pomegranate seeds.”
Not only did the ring contain the couple’s birthstones, the significance of the jewel chosen could have hinted to their royal future together.
“Garnets signify protection and are thought to promote confidence and mental clarity,” the expert concluded.
“Even though Kate graduated in 2005, and the couple married much later in 2011, this ring goes to prove that William was smitten with Kate even in those early days.”