Actually there are plenty pic for such M9, e.g.
http://www.phonesreview.co.uk/wp-con...evisited-c.jpg. Seems to be from non-US versions which could still be used in US.
From the pics of it, it seems to be machined perfect to HTC standard. I doubt it will be fake but you don't buy stuff like that from someone you don't know and have no recourse to return it if it is not what it looks like. Try eBay which gives you automatic protection.
Also, install apps to check processor used inside the phone. If it is Qualcomm processor, it is real. No fake phones can afford to use Qualcomm processors (majority of Chinese made phones use non-Qualcomm processors).