If it is genuine LMT M4 upper, that is a good buy
almost every dealer around sells that exact same set-up for $485
Which is in and of itself, disturbing. Its price fixing plain and simple, but that wasn't the question
You will be able to ID it as genuine LMT, 2 ways (or more)
1. LMT uppers have the LMT logo emblazoned on the shooters left side just below the rail and facing left.
like in this pic, borrowed from
BravoCompany Website2. The upper will be Duracoat-ed. This finish is at first glance almost like a bluing. Beautiful stuff
Then the M4 ramps will be visible, blah, blah, blah
edit in a couple things, svjos
welcome to AR15.com!
and unless you are Law Enforcement or similar, that upper will land you in court. Check local and state laws on it first
but you probably already know all that
good luck!