Who is offering it to you? Authorized Breitling Dealer, grey market, collector, Joe Blow of the street, on-line, in person, what? Does it come with box and papers?
Looks okay, but hard to really tell from one pic. It could be fake with a Gen dial on it. We do that all the time around here. So there is no real definitive way to tell.
Breitlings at 50% off retail brand new from ADs is not unheard of, but very very uncommon on this model. The Chronomat is Breitling flagship and most popular model. Other pieces like the Breitling Bentley jump hour you can find for 50%-70% off because they are very poor sellers s no one likes them.
Here is what I suggest