Two luxury Rolls-Royce Motors' cars used by the late Princess Diana during her visits to the United States, will go on public display at the Volo Auto Museum in Illinois, on Dec. 3.

The museum will showcase a 1996 Rolls-Royce Silver Spur III and a 1979 Rolls-Royce Silver Wraith, both of which are part of the museum's Treasures of the Vault collection that features cars owned or used by the rich and famous.

The Rolls-Royce Silver Spur III was used by the late Diana, Princess of Wales during her visit to Chicago in 1996. This car was the last Rolls-Royce to carry her in the U.S. whereas, on her first visit to the United States in 1985, along with husband Prince Charles, she rode in the Rolls-Royce Silver Wraith.

According to Volo Auto Museum, the 1979 Silver Wraith was acquired recently from Farley Berman, who owns the world's most extensive private collection of historic weaponry. Berman considered the Wraith to be most valuable piece in his collection and priced it at over $2 million, the museum said in a statement.

The British Embassy in Washington had bought the car for Royal visits. It took three years - and $300,000 - to fully armor it against bombs, bullets and gas, and the car weighs 10,000 pounds, the museum added. However, in 1996, when Princess Diana visited Chicago to raise money for breast cancer awareness, the Rolls-Royce Silver Spur III didn't have to be armored, for Diana was then divorced from Prince Charles and was no longer a part of royal family.

Both cars will be on display until Jan. 1, 2012, as part of Volo's Historic Trolley Tour. The museum also intends to undertake charity work through the displays, in honor of the late princess' commitment to the same.

The Volo Auto Museum will reduce each adult trolley admission by $2 for those who bring in a perishable food item. The food will be donated to the Northern Illinois Food Bank, the museum said.

From royal weddings to receiving visiting dignitaries, Rolls-Royce cars have been used on almost every occasion in the British royal family. Kate Middleton, the Duchess of Cambridge, traveled in a Rolls-Royce to Westminster Abbey for her marriage to Britain's Prince William in April this year.

Check out the photographs of the royal connection between the two royal clans.