How did epigraphists determine that various inscriptions were issued by the same ruler?

By matching the content, style, language, and palaeography of the inscriptions

The historical inscription (Source 10) does not directly mention the name of the ruler, Asoka. Instead, it refers to him using titles such as "devanampiya," meaning "beloved of the gods," and "piyadassi," translated as "pleasant to behold." The name Asoka is found in some other inscriptions along with these titles. Epigraphists, after analyzing all these inscriptions and noting their similarities in content, style, language, and palaeography, have concluded that they were issued by the same ruler.

In the inscriptions, Asoka claims that earlier rulers lacked arrangements to receive reports. When examining the political history of the subcontinent before Asoka, historians need to evaluate the accuracy of this claim. It is a constant challenge for historians to assess statements made in inscriptions, determining whether they are true, plausible, or perhaps exaggerated.