im presuming this is a 360... try burning a DVD and see if it plays a burnt game. if does, it's firmware modded
yes it is a 360,
Does it play a retail game disc? It could be that it was firmware flashed at one point years ago then it received the dashboard update that flashed it back to a newer stock firmware.
Oh also - very important - if this box hasn't been online in a looooong time and is still on the "blades" firmware for the love of god don't update it. You can JTAG that bastard and it will have a "real" mod