A postcard written by one of the Titanic’s most famous survivors just days before it sank has sold for £300,000 ($399,000) at auction.

In a note to the seller’s great-uncle dated April 10, 1912, first-class passenger Archibald Gracie wrote of the ill-fated steamer: “She is a fine ship but I will wait until my voyage is over before I pass judgment on her.”

The letter was sold to a private collector in the United States on Saturday, according to Henry Aldridge & Sons auction house in Wiltshire, England. The bundle’s price exceeded the original estimate of £60,000.

The letter is believed to be the only example of Gracie’s belongings from the Titanic, which struck an iceberg off the island of Newfoundland, killing around 1,500 people.

Auctioneer Andrew Aldridge described it as “a magnificent museum-grade piece”.

Gracie, who jumped overboard and escaped into a collapsible lifeboat that capsized, was rescued by other passengers in a lifeboat and taken to the R.M.S. Carpathia. When he returned to New York City, he wrote an account of his experiences, “The Truth About the Titanic”.

Gracie boarded the Titanic in Southampton on 10 April 1912, and was assigned first-class cabin C51. His book is considered the most detailed account of the events of the night the ship sank, Aldridge said. Gracie never fully recovered from the hypothermia she suffered and died in late 1912 from complications of diabetes.

The letter was postmarked Queenstown, Ireland, one of the Titanic’s two stops before it sank.