Yours is definitely an earlier model as the rear brake cable runs along the top tube rather than through the middle of it.The model after mine had a few other minor alterations such as using a grub screw for the seat post, but I don't think there were any major changes.
These are amazing bikes, I bought one a couple of weeks ago and it's incredibly quick and light:
http://dl.dropbox.com/u/58789818/Vitus%20979.png
Yours is definitely an earlier model as the rear brake cable runs along the top tube rather than through the middle of it.The model after mine had a few other minor alterations such as using a grub screw for the seat post, but I don't think there were any major changes.