Little help!! Is this an authentic IWC dealer clock?

[James 45]

So I just bought this clock (birthday present) and I pay for it and I get to thinking hey did I over pay? So I look for another one like it. I find the same seller selling another one very close to the same that started right after mine sold.
Then I look at finished auctions for the same clock and find every week this guy sells one or the other of these clocks. for around $400-$600. every week and had other brands There is a different date on the backs of them but how do you collect 6-10 of the same clock and sell them on a week for at least a year??

So if anyone know some thing I would like to hear
Thank you