1961 Topps - Horizontal Print Lines

I've noticed on a lot of '61 topps cards, it seems to be common to have black horizontal lines on the surface of the cards which look like print lines, scratches or smudges. Were these cards produced with these errors or were they caused my some erroneous handling or storage method? Also, will PSA significantly downgrade cards with these errors or what kind of qualifier will they be given?
Registry Sets
"Common sense is the best distributed commodity in the world, for every man is convinced that he is well supplied with it"
"Common sense is the best distributed commodity in the world, for every man is convinced that he is well supplied with it"
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Comments
Other ways it could have happened is the sheets were still wet and a sheet was put on top of the wet one.
1961 is not the only set where this has happened.
Someone that understands the nuances of printing could be more specific.
1954 Topps also has this problem.
The only qualifier that could be used is PD.
I have yet to see it used for that reason though.
Steve
"Common sense is the best distributed commodity in the world, for every man is convinced that he is well supplied with it"