I lost track of this story for a while after I heard the code of the public art piece by Ben Rubin at the Adobe HQ in San Jose was cracked. The winners have since been announced -- Mark Snesrud and Bob Mayo, two local research scientists.
Each of the four discs had four possible positions (horizontal, left diagonal, vertical, right diagonal) which together made up 256 combinations of its alphabet.
In addition to the discs there was a soundtrack with a low-power radio broadcast on AM 1860. It was possible to crack the code solely using the discs or the soundtrack. The soundtrack used a system where the first voice announced a word of the phonetic alphabet (alpha, bravo, charlie) followed by a second voice stating a number. In this case the first voice on the soundtrack represented the first two disc positions and the second voice handled the last two resulting in the same 256 character alphabet.