A water-damaged violin played by band leader Wallace Hartley aboard the Titanic goes on the auction block this weekend in the U.K.

The piece has been called the "Holy Grail" of Titanic memorabilia and is expected to bring the highest amount ever for an item related to the ill-fated ship – up to nearly half a million dollars, the auction house Henry Aldridge & Son said Thursday.

Known for playing on as the ship sank to help passengers alleviate the terror of the ship's sinking, Hartley and all the musicians died in the disaster. His body was recovered several days later with the violin attached to his life jacket.

“The band playing on was an incredibly selfless act,” said Andrew Aldridge of the auction firm. “William Hartley is an iconic individual. That is represented in the instrument.”