That is an aberrantly patterned amelanistic "Splotched" nelsoni. They are also known as "bullseye", and "spotted" nelsoni in the hobby as well.
That particular individual has a "vanished" phenotype to it's pattern as well. So it would be accurately called a vanished "splotched", "spotted", or vanished "bullseye" patterned nelsoni.
That snake is pretty thin too, so I hope it has a feeding response and will accept pinkies on it's own. This could very well be why someone didn't want to deal with it themselves in the first place.
regards, ~Doug

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"a snake in the grass is a GOOD thing" 
my website -serpentinespecialties.webs.com

