Two questions

[AWildSnorlax]

When I've seen people talking about steelbooks they say the steelbook is G1 or G2. What does G1 and G2 mean?

The other day I was in CEX and they had a copy of the limited editon of Fallout 3 for the Xbox 360 (the one with the Brotherhood of steel figure). It was for sale for ?22, but I got it for nothing because I had enough store credit to get it for nothing. I was wondering, is this editon quite rare? Because I don't think I've ever seen the 360 version on eBay, I've only seen the PS3 version or just the figure by its self.