From memory, the first Beale code was deciphered against the 'Declaration of Independance'; however, the document/book/whatever that the second (and of course more important [financially!!]) code has never been found or worked out.
One needs to look very hard at what literature was accessible in the US around that time (1820's).
I believe the 'stash' is currently valued at around US$20M.
The covering letter was lost hence that is why no-one has got very far in finding the gold!! It is believed the letter did contain instructions on how to decode the ciphertext.
[This message has been edited by Icarus (edited 01 July 2001).]