Genuine item, not a clone copy. Not tested extensively yet, but appears to be working - at any rate it talks to an X350 without trouble, and it's communicated with an older X300, although it indicates a communications issue with the X300 TCM. I haven't had chance to investigate this yet.
Overall: well pleased, and with shipping and import duty it was still cheaper buying from the US than the equivalent from the UK. How does THAT work?!