Well, this is quite fascinating:

The sale, which will feature additional items connected to cryptography, is scheduled for Nov. 20. RR Auction, the firm organizing the event, projects a final bid within the range of $300,000 to $500,000.

Alongside the original handwritten plain text of K4 and other documentation pertinent to the coding, Mr. Sanborn will also include a 12-by-18-inch copper plate containing three lines of alphabetic symbols carved out with a jigsaw, which he refers to as “my proof-of-concept piece” and that he used as motivation during the two years he and his team meticulously crafted the letters for the endeavor. The undertaking was demanding, precise, and nerve-wracking. “You could not afford any errors with 1,800 letters,” he remarked. “It could not be corrected.”

Mr. Sanborn’s ideal purchaser is an individual who will safeguard that secret. He also wishes for that person to be prepared to manage the process of validating potential solutions and sifting through those endless emails, possibly via an automated system.

Here’s the listing for the auction.