'A Charm Attended It ...'

 The Beale treasure cipher has been strenuously studied since the Beale papers were published in 1885. The papers are available as a PDF on the web, since the copyright has long since lapsed:

https://www.geneseo.edu/~baldwin/intd105/fall2016/TheBealePapers.pdf

The story is suspicious through and through - so many "friends of friends" involved, so many people (30!) involved in the original conspiracy with no leakage of information, the suspicious unanimity of trusting the money to Captain Beale, the instant jumping to conclusions of burying the horde in the hills of south Virginia, the lack of any sighting of Thomas Jefferson Beale in historical documents ...

The originator does spin an entertaining story, though - and he is a compassionate rascal:

"Before giving the papers to the public, I would say a word to those who may take an interest in them, and give them a little advice, acquired by bitter experience. It is, to devote only such time as can be spared from your legitimate business to the task, and if you can spare no time, let the matter alone. 

Should you disregard my advice, do not hold me responsible that the poverty you have courted is more easily found than the accomplishment of your wishes, and I would avoid the sight of another reduced to my condition.

... when your day's work is done, and you are comfortably seated by your good fire, a short time devoted to the subject can injure no one, and may bring its reward."

Josh Gate's Expedition Unknown had a very interesting episode on the cipher, with the last 10 minutes in a devastating interview with a cryptologist named Todd Mateer. Mateer did some very interesting things! - First he went through the analysis of cipher number 2, and showed that the decryptor and the encipherer had to be the same person, because the encipherer made fatal mistakes that the decryptor was nevertheless able to follow with ease!

The second thing he talked about was taking the deciphering engine developed to follow the cipher 2 decryption, and feeding cipher 1 into it! At one place deep in the document, the sequence "ABFDEFGHIJKLMMNOHPP" shows up - what you might expect a bored hoaxer would do when he was tired of generating random patterns. And he notes that cipher 3 is too short to have 30 family addresses and extended family member notation.

I don't think this treasure exists in the same way that some of Roger's other treasures do. Nice story, though.