BOSTON — A vital piece of the puzzle to unravel the last unsolved secret message within a sculpture at the CIA headquarters in Virginia has fetched nearly $1 million at auction, as announced by the auction house on Friday.

The successful bidder will have the unique opportunity to meet privately with the 80-year-old creator of the sculpture, where they will discuss the codes and charts. This interaction continues the artist’s long-standing tradition of engaging with enthusiasts and aspiring cryptanalysts.

The collection, owned by Jim Sanborn, the artist behind the Kryptos sculpture, was purchased by an anonymous buyer for $963,000, as reported by Boston’s RR Auction. The archive includes significant documents and coding charts associated with the sculpture, which was unveiled in 1990.

While three of the encoded messages on the 10-foot-tall sculpture, referred to as K1, K2, and K3, have already been cracked, the fourth, known as K-4, remains elusive. Experts and dedicated enthusiasts alike have been stumped by this conundrum etched into the S-shaped copper screen.

The sculpture itself resembles a sheet of paper being pulled from a fax machine, with one side displaying a series of staggered alphabets crucial for deciphering the quartet of encrypted messages located on the other side.

One person has contacted Sanborn regularly for the past two decades in an effort to solve K4, and Sanborn received so many inquiries he started charging $50 per submission. Sanborn decided to sell off the solution to K4, putting it in the hands of someone he hopes will keep its secrets and continue interacting with followers.

RR Auction said the winner will get a private meeting with Sanborn to go over the codes, charts and artistic intent behind K4 and an alternate paragraph he called K5.

The purchaser’s “long-term stewardship plan” is being developed, according to the auction house.

Sanborn’s roughly 50 public sculptures include a memorial for a 2019 mass shooting in Odessa, Texas.

The archive auction was almost derailed in September when two Kryptos sleuths found Sanborn’s original scrambled texts in the artist’s papers in the Smithsonian.

The sale went ahead but was changed from offering only the secrets to K4 to selling his entire archive.

“The important distinction is that they discovered it. They did not decipher it,” Sanborn told The Associated Press. “They do not have the key. They don’t have the method with which it’s deciphered.”