Waiter... There's A Hair In My Slab

On their first generation slabs, not their second generation.

It's not the graders... if you've ever seen the video of how the graders work they sit on comfy chairs in a dark room with good light and they handle the coins in boxes of plastic flips.

After grading [and for those orgs who practice it finalization and QA] the boxes of coins get handed off to somebody else who assembles the coin into the case and uses a large industrial machine to ultrasonically weld the case shut.