Compare them.
As I said before, I bought a real one - depotted and dismantled the ENTIRE thing and compared. All 3 were "presumably" from the same batch. On comparison the two bay ones were different to my MAC bought one and the two ebay ones were inferior quality. Having said that it wasnt until I had the store bought one beside them that I knew for sure it was a fake - these are pretty good copies actually. However, on compariosn and close inspection the pots were substandard moulding and even the aluminium pan was substandard in quality and thickness - the fakes pans are easier to bend, and thats because they arent as strong and have much thinner walls and base. They also scratch fairly easily - but if you were just looking for the pan to be flat then you would probably overlook all those flaws.
The colour is also different - but it IS close sp I could see how people missed that, its very close actually. The texture IS different though, the fakes are softer and ironically enough have BETTER payoff than the real one did.
The pot is easily enough overlooked unless you look carefully at specific markers - which I wont be posting here - but if you saw the comparison pics I took of them then you would know in a hearbeat both the ebay shadows ARE fakes. These are also the SAME shadows that were doing the Costco rounds so if you bought your e/s at Costco I suggest you consider discarding it.