The foundation inscription
Original — Middle Bulgarian
† Въ лѣто ҂ѕ҃ѱ҃л҃ѳ҃ индикта д҃ отъ Богомь въздвиженіѣ царь Асѣнь блъгаромь и грькомь и прочимь странамь постави Алексѧ севаста и създа сеи градь
Translation
In the year 6739, indiction 4, raised up by God, Asen, tsar of the Bulgarians and the Greeks and the other lands, appointed Alexius the sevast and built this fortress.
Note: The year 6739 from the creation of the world is 1231. Biliarski notes that Алексѧ and севаста are both accusative, so the tsar appointed Alexius — who already was a sevast — to a post; he did not confer the rank itself. The imperial style, a year after Klokotnitsa, is the same claim the Tarnovo column makes.