It's a 2 year old model that's long since discontinued (2 years is as good as 20 in the world of mobiles). If your brother wasn't too fussed, I'm sure he wouldn't mind you opening the box and having a look.
It might have a sim card in it already. If it's an O2 sim, then the phone is not network locked. Similarly, if there is no sim at all, then it is probably a sim free model with no network lock. Anything else, then it's probably locked to the respective sim that it comes with. If there is genuinely nothing at all on the box that would suggest a network then the only way you're going to be sure is to open it and have a look.