I wonder right away about the rim around 6 to 9 o'clock on the obverse and the color looks real funny to me.
That's what worried me the most, along with the denticles on the reverse from 3 to 6 o'clock. Somebody popped for it at $325, a few hours after it was listed as a BIN. We'll see what happens in the feedback. If it's a real coin, someone may have gotten a good deal.
That's nothing really unusual, the coin just isn't well centered. On a well centered coin the rim is the same width all the way around. On coins that are not well centered one part of it will be wider than the rest, while directly opposite that wide area the rim will be narrower than the rest. This is something that is actually so common that being well centered is a grading criteria. Unfortunately it is a criteria that many have forgotten in today's world.
Unless a fake is crudely manufactured, it's often difficult to tell if a coin is authentic from photos alone. Few, if any, modern forgeries are cast. Most are die struck and artificially aged, sometimes with dramatic effect... making it a "less than easy" task to determine authenticity, even with the coin in hand. As far as the OP's coin is concerned, it bears little resemblance to the fake '09'S IHC's I've seen. So I'm leaning towards genuine; but unless the current owner sends it off for grading, we probably will never know.
The odd color and poorly centered strike are good reasons not too like it. I think it is a genuine coin, not sure about the MM. If I were going to try to add the "S", I'd start with a different base coin.
I don't see any of the telltale signs of a cast counterfeit. For instance, I don't see any casting bubbles or loss of detail as you see in a cast copy. You could get a better idea by looking carefully at the edge for the cast seams or tooling to hide them. The color looks a bit off, but that could simply be recoloring. The only thing that really left me scratching my head was the denticles on the reverse around 5 o'clock. They look odd.