A quick physical comparison between a genuine Hakko FX-888D (purchased from Element 14) and an exceptionally close knockoff from eBay.

Things that might indicate you have a fake:
* The box is not made from recycled material - it has no smell, no flecks of recycled material.
* The soldering iron hand piece has a non-silicone strain relief.
* The stand doesn't have a sheet metal insert.
* The screws holding the power cord into the power supply have a sharp tip, i.e. aren't self tapping.

The fake is amazingly close to the genuine article. The box is nearly perfect (other than the cardboard it's made out of). The rest of the packaging is bang-on.