Difficult to tell from this picture. Looks like it could be an artifact from sharpening the image, either in-camera or in post-processing.
au57---nice luster, full horn, full tail---wait and you remove it from a slab why? rim is fair---wait it was already graded?--oh---your hoping for a higher grade==$$$, yeah send it in
I keep saying that USB cameras with their 1.3 - 2.0 mpixel chips are worse than shooting a good phone camera through a loupe. The only way they can get higher magnication is by making up non-existent fake pixels in software. Quite a few people see doubling and errors from artifacts.