I think the offset into the elected (or otherwise) ruler, by name. Confer the inscription atop the Pantheon "M Agrippa L F Cos Tertivm Fecit" where the gist i

I think the offset into the elected (or otherwise) ruler, by name. Confer the inscription atop the Pantheon "M Agrippa L F Cos Tertivm Fecit" where the gist is M Agrippa <whenever L F Cos the third> made (it). From Wikipedia's page on the Pantheon: "M[arcus] Agrippa L[ucii] f[ilius] co[n]s[ul] tertium fecit," meaning "Marcus Agrippa, son of Lucius, made [this building] when consul for the third time.