Given the importance of Pauly's work (Wikipedia, Wikisource), I assume it wasn't written in gibberish by a madman. That said, what secondary or tertiary sense does the German real or Real have that makes the titles Real-Encyclopädie der classischen Alterthumswissenschaft in alphabetischer Ordnung and Realencyclopädie der classischen Altertumswissenschaft make any sense at all?

The only Wikis that seem to provide a gloss are Spanish and Russian, which both use cognates. Spanish real could obviously mean royal, which would make sense. The Russian translation and Wiktionary's treatment of German real and Real don't seem to allow that possibility, though. Cursory googling turns up a few other books with similar titles, so it's not just Pauly's eccentricity.

So what's going on? Is it just an archaic way of saying "scientific dictionary"? or what would a decent modern English gloss of these titles be, distinguishing the intended sense of a "real encyclopedia" against whatever it considers its inverse to be?