The thermo is coming from Partsworld-Uk who have been mentioned loads on here and have been talked about positively by many members, so I trust what they are going to send will be the proper part.
Making a pattern part is one thing, trying to pass it off as genuine and illegally stamping another company logo on something is something else entirely!!
Generally i would say the easiest way to tell is the box it comes in, not fool proof obviously but genuine parts come in not a blank white box..