I've not seen a real 3" THDP with the dimple or indentation below the bolt hole as shown in your photo but I could be wrong. With all the subtle differences from pipe to pipe depending on who made them and when they made them it's difficult for the average person to know for sure. There was a good thread made on the differences between a "real" THDP compared to the other "Terry Houston style" downpipes but since most of the photos in the thread were lost, it's value is diminished.
The main reason (besides the name alone) people will pay good money for a "real" THDP is because it fits very well and the quality of the stainless is very good, but that's not to say other well made DP's like ATR, Mease, etc. won't perform equally as well. You just have to know what to watch for. Example, ATR made a very good DP but it had a problem with a sticking puck. Once you got that problem area addressed, it performed as good as any other well made pipe. You definitely do not have a cheap Chineseum piece so if the fit is good I would do as others have said - clean it up, make sure the puck swings freely, and run with it.