I'm nowhere close to being a pleco expert but I have something similar.
Could it be a washed out / brightly lit version of this? Can you get a different photo? Not sure about that but here is my White seam-bad phone pic but u get the idea.
This is a blue seam ancistrus, and there are white seams, too. L183
Lots of spots, bluish (or white) edging to the dorsal and tail.
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