My original trio of pure endlers reproduced on AVERAGE one fry a day over the course of a 3 month period. Mine came from a auction run by the Minnesota Aquarium Society, we are very particular on proper labeling. They were labeled as pure so must I trust they are pure. Last auction I saw some fish labeled as hybrid sword/platies and it was very obvious that is what they were. Generally the color pattern on endlers and guppys is very different, along with fin shapes, behavior, and size.
This is what my endlers look like.