I don't own anything as fine as a Grade 5, but both Syracuse L.C. Smith Quality F hammergun and Quality 2 hammerless, which were the lowest grades had 22-24 lpi, so I have to agree with what Dick has said. These were special order guns, and you could get what you wanted on them.
Dick was also right about both books, there are vast mistakes in them, but without these there was no foundation to go on and compare.

David