Does it have the serial number? Could run it through the decoder. http://www.chipmunk.nl/klantenservice/applemodel

Other than that I don't think you can tell. You'd know if it was a Quad, it'd have a huge LCS in there lol.

You sure it's a 6600LE and not a 6600? The LE was standard on the 2.0, but someone could have stuck it in the 2.3.