The latest letter in the corpus and its only Parthian one: King Artabanus III of Parthia — writing under the Arsacid throne-name 'King of kings Arsaces' — answers the magistrates Antiochus and Phraates and the city of Seleucia on the Eulaeus (Susa) in A.D. 21. The matter is a routine civic one carried up to the king for confirmation. Hestiaeus son of Asius, a citizen and a member of the court orders of the 'first and most-honoured Friends' and of the Bodyguards, had served as treasurer in the year 329 (Seleucid reckoning) with exemplary honesty, sparing no expense and twice going on embassy for the city. When the office fell due again for the year 332 he objected that the constitution barred him from holding it twice within three years; but the city, valuing his record, re-elected him, and referred the case to the king. Artabanus rules the election valid (κυρία), forbids any prosecution of Hestiaeus for the repeat tenure, and sets aside any contrary ordinance. The letter is inscribed in Parthian-chancery 'barbarian Greek' on a statue-base from Susa (now the Louvre), and survives only in Cumont's 1932 editio princeps — so it carries the corpus's highest reading-uncertainty, here disclosed.本集最晚之书信，亦唯一帕提亚之书：帕提亚国王阿尔达班三世 —— 以阿萨息斯王朝尊号「万王之王阿尔萨刻斯」行文 —— 于公元21年答埃乌莱奥斯河畔之塞琉西亚（苏萨）之执政官安条克与弗拉阿特斯及该城。所议乃一寻常城务，呈请国王核准。阿西俄斯之子赫斯提埃俄斯，本城公民、兼属「首要尊宠之友」与「侍卫」之宫廷阶级，曾于（塞琉古纪元）329年任司库，廉洁堪范，不惜耗费，且两度为城出使。届332年此职复缺，其以城制禁三年内两任同职为辞；然城邦重其往绩，仍选任之，并将此案呈王。阿尔达班裁定其选任有效（κυρία），禁以重任之故追究赫斯提埃俄斯，并废除任何相悖之敕令。此函以帕提亚文书之「蛮族希腊语」刻于苏萨一像座（今藏卢浮宫），仅存于 Cumont 1932年首刊本 —— 故为本集读之最不确定者，于此披露。