According to diamond expert Max Stone, of jewellers Steven Stone, this ring is thought to be worth a whopping £30million.
Meanwhile, Grace’s first ring could be valued at around £15,000.
Max said: “While it’s incredibly difficult to value a ring without seeing the original item in colour, the fact that the ring was designed by Cartier and features heirloom rubies, which look to be around 1.5 carats, along with 1.5 carats of diamonds, suggests it could be worth over £15,000 today.
“Although Grace Kelly received the incredible 10.5 carat Cartier diamond ring shortly after, which is now one of the world’s most famous pieces of jewellery, the rubies featured in her first ring are likely to be very rare and of the finest quality.
“Rubies are also soaring in value right now, so it’s likely the value of this ring will increase even more over time.”