It is hard to say, since true, wild type, endlers have been line bred without being mixed with guppies, but my guess is the only thing pure about your endlers is that the line they are breeding from breeds true. A line can be thought of as pure by some breeders of crosses simply because they don't see any variation to speak of in the fry. I maintain two separate colonies of wild type endlers and the color ahead of the dorsal does not bother me. The peacock spot also is not a problem but I am concerned by the apparent vertical stripes in your second picture. That smells of tiger endler to me, a definite hybrid though a very pretty one.
Does the seller have any traceability back to a wild collection the way I do? In my case, the fish can be traced back, quite readily, to a collection in 2000 by Armando Pou in the Laguna de Los Patos area of Venezuela. Collections since that time are almost non-existent because the local government tries their best to prevent such collections now. The government of Venezuela is especially difficult for an American collector to deal with due to prejudices that exist between the countries. There is a total of 1 other keeper between that collection by Armando Pou and my own first tank full of breeders. I have maintained mine meticulously clean since I got them in 2003 so I am confident when I certify to someone that they are "pure" by any standards that exist.
On the other hand, people like Adrian Hernandez have line bred strains of pure endlers to emphasize one or another feature that exists in the wild fish and can also trace their fish back to the wild. Adrian has some gorgeous fish to sell that are derived strictly from wild type fish but no longer resemble their wild parents very much. It is just possible that the fish you have came from such a strain.
