'so long before as his [Horace's] and Augustus's time, who marmoream reliqiiit Romam as he himself did testify, and I cannot perceive but the heads on his and his succesors' coins to Nero, when they commonly fix the standard for elegancy in re metallica, are as bold and Just as after; but the reverses have rarely so many figures on them, and I believe their medaglions are rarer; yet some of the few brass family pieces which I have seen in my lord Coleraine’s collection, the Agrippina in brass with Neptune on the reverse, the Augustus of the same size with an eagle on the reverse, in my own few specimens of such remains of antiquity, and civitatibus Asiae restitutis there also, a compliment to Tiberius, which Mr Secretary Addison under Naples takes so much notice of as to give a print of it, are proofs [of the date of a bronze bust] ... in a reverse of a mezzo-bronzo, a complex figure of that prince, both as the God Phoebus and the Fidler Nero, as he appeared on the stage...'
(Nichols 1781-1790, pp. 52-6; Burnett 2020b, p. 1660)