His first major paper,[1] published in 1848, presented such convincing epigraphic proof to this effect that the predominant academic opinion which had tentatively located Flavia Solva in the Zollfeld in Carinthia (actually the site of Virunum), quickly accepted it.
[4] However, the central project of his life - a codex of all epigraphic finds from antiquity made in the area encompassing today's Austrian province of Styria and northern Slovenia, documenting about 600 inscriptions at 183 sites on its 728 pages - remained unpublished; the manuscript is kept at the University of Graz.
Knabl's painstaking work, sustained over three decades and always adhering to the scientific standards of his time, earned him acceptance among accomplished historians such as Alfred von Arneth and Theodor Mommsen who in their official statements spoke highly of him.
For example, Mommsen (then a 40-year-old assistant professor in Berlin) wrote in a letter to a friend dated 8 September 1857: "Number One among the sages in Graz is the priest Knabl, an aged type of 65 who has applied himself to the stones in his late years.
If he learns of a Roman stone somewhere in Styria he will instantly travel there with comical enthusiasm, and will then lie there reading for two or three days; with a strong pretense at scholarship, but with even stronger respect shown towards myself whom he eagerly kisses the hands, collecting fragments for my biography.