Ive never seen a led panel before, so I have no idea either. Im guessing if it doesnt have those two high voltage wires, or if you dont see any sort of boxy looking step up transformer/inverter, then it might be led. Id love to check out your install one day though. Your screen fab looks great from the pic...doesnt look like you had to use any bondo at all.
I can tell u that it definately has those high voltage wires, also it has the inverter as well, so i'm guessing it might not be LED backlit after all. Anywho, give me a shout if you want to have a look at it some day, btw, i did have to use epoxy to put mine together (bondo would've probally worked about the same.