It looks like many tryptamines have the same or similar reactions with all the alkaloidal colour reagents.. Although I never found results for Mandelin. Simon's would be able to tell NMT from the others, but dang that's a really good question. I've also been wondering if there was a simple test for discerning 4-HO subbed tryps from their acetylated cousins.
A melting point test could be useful here. It's a relatively cheap & easy test that is good for confirming sample purity, and if the temperatures are already known then it can also be used to presumptively confirm sample identity. I've never heard of or seen a database for tryptamine melting points, so that might be a project worth working on.