I have a number of non working Xbox 360s from various parts of the word. Unlike sensible machines from say Nintendo and Sony who mark on the machine what region it is, Microsoft don't. So I need to tell which machines are American, European and Japanese and looking at the back doesn't tell me squat.
Calling Microsoft will tell you what the system is. Just gotta give them the serial. They will tell you the region, 1 2 3 4 etc..
Talk To Microsoft in Your Local Region They Will Run The Serial Numbers and tell you the region of the paticular console
I can't believe there isn't an easy way to tell the region of the console without phoning up microsoft and quoting serial numbers, I am not taking 3 or 4 but more in the 30s or 40s, so going through all of them is a pain.
You can differentiate the regions on the original box on the sticker, though this doesn't help you in the slightest. Maybe try here: http://www.360drives.com/list type in some details and it might come up with something.
Well, you could at least tell what region one isn't by popping in a game right? Guess that doesn't narrow it down unless you have games from many regions.