Joe Nacca...I just bought a bunch of books from him and I'm not sure if 10% matched up with the reported grade.
I used to buy books from him in the 90s, when he had a lot of scarce and under-priced stuff. I learned to expect 0.5 to 1.0 less in grade than he advertised. When I called him on it he said everyone else was under-grading...I don't buy from Joe no more... but back in the day he was a good source, as long as you knew how he graded.
I think these days, at least in his eBay listings, he has been shying away from listing an exact grade and has a lot of hedging language in his descriptions. Maybe he's been burned by too many returns.
What's his ebay name? I'll avoid it...