Recent Stats from 1974 Kellogg's - When Were Nine-Pocket Sheets Created?

I've been seeing consistently cracked cards in the 1974 Kellogg's set.  Which ones?  The first nine.  Did nine-pocket sheets come out that year?

Here are some PSA stats for 1974 Kellogg's cards.

Not counting variations, every card from #10 to #54 has at least 30 PSA 10s.  Here is a breakdown for the first nine cards.

#1 Bob Gibson - 10

#2 Rick Monday - 6

#3 Joe Coleman - 28

#4 Bert Campaneris - 23

#5 Carlton Fisk - 15

#6 Jim Palmer - 54

#7 Ron Santo - 14 (total of both variations)

#8 Nolan Ryan - 25

#9 Greg Luzinski - 29


Starting with card #10 things change a lot.  Are there more difficult PSA 10 Nolan Ryan's from issues that were distributed nationwide?