Probably some mix of koi or marble and the fins are probably an attempt at a veil tail.
When the different types are being crossed and bred for certain features occasionally there will be the odd or unexpected result.
This is how different strains, fin shapes and color morphs get started.
It's a line bred angel. It was just bred to have the long fins and white marble color pattern. It's a nice find tho. Just be warned tho if you have any fin nipper types of fish in the tank that he is going to be a prime target.