I will contact trek to get proof, but I would agree that it does look like a 2004/2005 bike.
If I had known this for certain, I would not have paid more than £800 to be honest. It is worth a bit more than others of that age given that it has all dura ace components.
I asked the guy loads of questions and he definitely said that he believed it was four years old. But he did add that it was the model after Lance "won" his 7th tour, which after some research would make it a 2005 bike. However, is it reasonable to expect that the buyer check this? I asked a direct question and got an answer of four years old.
I have contacted him regarding the age thing and I am awaiting a response.
I could be a genuine mistake on the guys part but he did say the he thought that the bike was four years old.