David,
Maxillaria schunkeana (need that 'c'

) is a species hailing from Espírito Santo, Brazil. It has very dark purple flowers, considered near black. Here is the publication data:
Maxillaria schunkeana Campacci & R.A.Kautsky
Orquidário, 7(4): 136 (1993).
I considered
Max. variabilis, yet is is native to Mexico, not Peru, so that is not the species either...
Will keep looking though...
-Pat