Yes, it's an official model, however probably the most rare as well. There where only 300 made, and then they broke the mold. They where then handed out to certain GW managers as a Gift.
Now, they made 300, and I've seen at least 4 conversions using the model, that makes only 296 left, max.
And guess what, I've got one of them.
Check out the thread 'Fantastic News' in the Feeding Grounds.