What does N.P,. np. in a citation

I have noticed that for many of my citations, in the Bibliography line, there are these letters at the end of the entry, N.p,.N.p.

Does anybody know what that is about?

A quick search yields a possible usage as:

“N.p, n.d.” which means no publisher and no date, respectively.

“n.p.,” which must stand equally for “no place ,” “no publisher,” or “no page,” but in English publications “n.p.,” used correctly, is more likely to be understood; CMOS (Chicago Manual of Style), therefore, recommends “n.p.” Note that “n.p.” can stand in for both publisher and place, if neither is known.

Generally in genealogy it means “Not proven”.

Is this another trans-Atlantic difference in semantics? In my albeit limited research on both sides, I only recall the use of “n.p.” in the context of citations as @kbens0n posted.