Hey I'm allowed to be wrong sometimes too
Back when I used an 810, which wasn't that long ago, all the manuals I had were not sealed. I remeber at that time people were calling the manuals "sealed", but none I ordered were sealed.
2 lessons there,
1) until someone sees a 510, they may not know what sealed is.
2)
make sure when you order the supplier knows what they are stocking, as the old non-sealed stock is still going to be out there.