1950 Bowman Baseball question - How rare are the No Copyright variations?

How long has PSA graded the No Copyright variations, and are they as rare as the pop. report suggests?
Collecting 64, 66, 67, 70 & 71 Baseball. Cubs, wax, cello & rack baseball.
0
Comments
There are now 4 cards in this set w/o Copyright. PSA must have just started distinguishing the difference.
In no way should pop report reflect actual numbers.
Same thing with gray/white backs.
I would be interested in knowing if no CR were first runs.
1948-76 Topps FB Sets
FB & BB HOF Player sets
1948-1993 NY Yankee Team Sets
Bowman Baseball -1948-1955
Fleer Baseball-1923, 1959-2007
Al