The only person clearly designated as such in the NT is Blastus,
ὁ ἐðὶ ôïῦ êïéôῶíïò ôïῦ âáóéëÝùò
(sc. Herod Agrippa i.), whom the Tyrians and Sidonians persuaded to befriend them against the king’s displeasure at Caesarea, and to obtain peace for them ‘because their country was nourished by the king’s country’ (Act_12:20). The office he held would obviously involve great intimacy and influence with the king. Erastus, who is called ‘the chamberlain of the city’ in Rom_16:23 (Authorized Version ; Revised Version ‘treasurer’), held a different office (see Steward). The eunuch of Act_8:27 ff. also held a different office he ‘was over all’ the queen’s ‘treasure’ (see Ethiopian Eunuch).