[1880nonsports]

(no not the one Kawhi Leonard hit to win the seventh game at the last second) but based on all the scans posted I think it's almost a certainty that there was just excess paper removed. Possibly due to the sticky finger theory as many times that's the case with antique paper in the form of trade and insert cards that have been glued in a scrapbook by a child with six fingers BUT such a condition would likely result in the part of the layer underneath coming loose from the card when removing it.
Particular to this issue and quite a few other "N" cards is that they were glued into stock or company issued albums - often contemporaneous with their issue. The company issued album pages had a very porous texture and the inking on the N162's (and others) was layered on the surface. Over time small bits of paper fiber from an opposing album page might adhere to the front of a card as the items are exposed to aging and varying storage conditions - often while pressed together in a box with great great grandpa's stuff in the attic for generations. When the excess fiber is removed by soaking (NOT always possible) - the underlying inking may exhibit any number of differences - sometimes subtle on a micro level when compared to the unaffected surrounding neighborhood under scrutiny and at other times more obvious. That's pretty much what I see here. I have seen quite a few examples of this in my 20+ years of collecting this stuff.

SOAKING CARDS HAS BEEN AN ACCEPTED PRACTICE BY A WIDE MAJORITY OF HOBBY PARTICIPANTS at least as best I can judge since I started collecting. I would imagine more than 80% of 19th century tobacco cards were soaked from an album and likely significantly more. You would have a different hobby if soaking was verboten. If there's no paper loss from the machinations whether to the printing on the back or a depiction on the front - I find no issue. It's up to the consumer.

no guarantees whether written or implied