Hanayama released the puzzle this past spring and it's available from shops for a reasonable price. So what is the difference and which is which? In the photo above, the Hanayama version is on the top. It has 2 pieces that have been fused together, unlike the original which is polished so well you can't see the seams. Other than that, there is no difference. The puzzles are the same size and weight! (Andreas!)
Hanayama rates these as a level 3 and I'd guess that would be about right. It's not a difficult puzzle to solve, even I managed it without too much difficulty!
And now, one more photo. I found another treble clef puzzle I found in one of our local shops. Now I'm going to go out on a limb and say I don't think this is a copy. I purchased it after returning to HK from the 2009 IPP. As you can see, it isn't exactly the same. Unlike Harmony, this puzzle has an open loop and a ring that needs to come off. Different enough I would say. The challenge isn't the same as Harmony, but I would say it's on par as far as difficulty is concerned. Where it can be purchased from or what it is called, that I don't know.