Apparently I like to jump to conclusions before getting the whole story.
You'll see in my previous post that I assumed that people had gotten the sixth code through less than honorable means.
That's simply not the case. Two people deserve very honorable mentions here: Laurabelle at the HETFET forums for figuring it out, and Alison, who's been commenting on this blog, and has repeatedly suggested there might be something in the fact that 'silver nitrate' has been popping up a lot lately. In this post she actually gave us the key to the sixth code, and I brushed it off.
Alison, I apologise for my ignorance, I underestimated the game :)
So, to the solution. Silver nitrate popped up in the latest news story from HETFET, but in more than one way. You'll notice the name of a woman - District Attorney AGatha N. Olan. I originally dismissed this as a sly reference to The Dark Knight viral ARG (Harvey Dent is a DA, Christopher Nolan the director). Maybe it still is - but it's predominantly a clue. Her initials.
The story also links to Uthyntrol where those with a keen eye (i.e. not me) will see that in the bottom right of the screen, the website has been updated so that the active ingredient reads 'SILVER NITRATE' rather than 'pending FDA aproval'.
Longer story short, the chemical compound for Silver Nitrate is AgNO3.
A periodic table will give you the answer you want.
Ag = 47
N = 7
O3 = (8 x 3) 24
And there you have it - 47-7-24
Take that to The Secret Device and reap the rewards.