This is the Mark IIB pre-heresey Land Raider.
It is part of Mike Sharpe’s superb Space Wolves army, which was on show at GamesDay 2006.
The model is available from Forgeworld and is a very nice kit. I have one but have not yet started it. It is based on the plastic Land Raider kit, and the model is very similar to the Epic Land Raider.