There are 2 "kinds" of Altums being listed in the trade however, there is also debate as to whether they are both P Altum. P. altum is said to come from the Rio Negro and surrounding areas while the "imposter" is from Peru and is a sub-specie or color variant of P. scalare. I tend to hold that the Peruvian Altum is not P altum but a scalare as I have brought in many scalare in the past from Peru and never had an Altum amongst them.
Also, in an Altum, the facial features are different than a scalare and these look to have scalare faces. I happened to find this post that might help you distinguish them:
Altum versus Scalare angels, how to distinguish them
Hope this helps.