That's strange, because I got mine pretty damn close to launch too.. But then again I have the PAL game which isn't rated by ESRB but some British rating system. It says 15+ on my box..
The logo is a little red circle, I think it's called BBFC or BCF or something like that, it's hard to read it..
Yep my old version says 15 the GotY ed I just got as a back up again says 15, on Amazon as posted above it has a 16 rating.
I think BBFC stands for the British broadcasting film censor, it rates all media from TV's watersheds to computer games, from universal to 18.
I'm not 100% sure but I think anything above an 18 gets baned in this country.
These were brought in I think to appeal to a campaigner for decency, one Mary Whitehouse between the late 60's to 70's but am not sure about the date myself.
Untill recently even swearing was prohibited on tv, one reason shows like Red dwarf, the fast show and other comedies even during the late 90's made up swear terms such as Smeg.