Now i'm back, but i'm not definitely sure if i can provide helpful information, because there was no MDMA for a comparison test available (only a tiny bit of the residue of a previous acetone wash for cleaning MDMA... i had hoped that the residue still contained some MDMA [which it surely did], but obviously it was way too less). So i used some of the residue.
I set up two KMnO4-solutions, heated them until almost boiling and dropped each substance in one of the 25ml-beakers.
The MDMA-beaker produced a change in smell, but it was almost unnoticeable. I'd say it was somewhere between cherry (?) and moldiness. The solution stayed violet as it was (as i said, way less than enough substance...).
When i dropped the substance being sold as MDPV into the second beaker (i think it was some 20-30mg; was too lazy to get the scale and didn't find it to be neccesary), it started bubbling instantly and again, some smell occured (this time stronger) which remembered me to a mixture of something floral but at the same time moldy with a decent odor of a senior person (ya probably know what i mean, hehe. Just like entering the house of my old grandma.
Sorry, grandma, if you read this [probably not], but i couldn't find a better comparison) and maybe again this cherryish odor, which seemed to only appear right after addition - later, the other described smells were superficial.
All in all hard to describe, as another aggravating circumstance is the fact that i'm using nose drops since months, so my sense of smell may be affected a bit...
Something that may be worth to mention:
As the peevee was added to the KMnO4-solution, it (the soln.) did change its color - from violet to dark-brown. And it was not anymore that clean as before; it became some kind of flaky/grainy! Could be possible that it was due to the peevee being grainy/powder and i just saw that in the solution, but it appeared to me that there were more crystals/flakes in the solution than the educt-peevee-substance was.
Also remarkable: there was something on top of the brown solution which i would describe as some kind of layer (there was not enough substance to produce that much to really identify a layer sitting on top). Could be imagined like a thin film with slices sitting on top, and it appeared (i hope that's understandable - language barriers again, but i'm trying hard...) like that film/layer which sometimes can be found on water puddles near a gas station, which kind of shines in different colors, at least it didn't appear to be homogenous.
Due to the fact that the color of the soln. changed immediately after "peevee"-addition, i'd say that there was definately a reaction going on. But yea, there are lots of possible substances which have an affinity to being oxidised. So still the problem is that i can't be 100% sure about the odor, although it seems to be at least similar to what e.g. wikipedia says... but it also says something about a vanilla-esque odor, which i definately didn't recognize.
Okay, i hope that some of these points could give a clue for what this might actually be. Maybe F&B finds his way to this thread, as he was trying the same thing and obviously has more knowledge about this than me.
Greets!