US Perfin Nsc Pattern (N150) Question

I am trying to figure out how to catalog these two perfins (see image of the backs below; note that the fronts of the stamps are inverted). As the images are of the backs of the stamps, I believe that the pattern should be read right-to-left: "CSN". I did a search of the new 2018 catalog and did not find a "CSN". However, I did find, "NSC". Based on the hole counts it matches N150, in that regard.

Where I am getting confused is that the catalog shows N150 with its letters descending from left to right. For the stamp on the left, that would mean the stamp was punched from the back -- I think. For the stamp on the right, it would have to have been punched with the stamp inverted -- I think.

So am I correct? And are these sorts of perfin variations normal? And while the variations are not noted in the catalog (unless I have failed reading comprehension), are they typically collected as "different"?

Thanks for the help.

Perhaps seeing the cancels on the front of the stamp might help the investigation?

Users often folded the sheets of stamps like an acordian, then punched several layers at once. Thus half would be punched from the back side. They can be found in any orientation on the stamp. It can be a challenge to ID perfins containing mirror-image letters.

Variations normal - most collectors are content with one copy regardless, but of course some want all orientations.