Any attempt to research Giuseppe Giusti online is frustrated by his two far more famous namesakes, the mid-19th century poet and the contemporary producer of Aceto balsamico di Modena. Roberto Marcocci lists him, but doesn't have a single career fact on him – which makes it highly improbable that he had any stage career at all, or at least not under this name.
All that Marcocci lists about him is one recording, and that one was mislabeled by G&T (G. C. 52759, mx. Con 222), back in October 1903: "Nerone (Rubinstein) – Strofe", which would be what the original French libretto calls "Stances": Ô lumière du jour. Marcocci has Giusti accordingly as a tenor. In fact, though, the aria recorded is the "Epithalamium": Hymen, hymen, since Giusti was a baritone. And what a baritone he was! The recording is outstanding; a serious competitor for Battistini, who left another fantastic recording of that aria.
The Hymen, hymen is Giusti's only operatic recording; but not at all his only recording: he made a documented minimum of 142 recordings, the majority on Bettini cylinders (which means that almost certainly, he must have made lots more). Everything else than the Néron aria is canzoni: from countless Neapolitan songs of the day (many of whose composers are not even known) to everything that's still famous in Neapolitan music, and to Musica proibita and Tosti songs: excellently delivered, as well.
So who was Giusti? For a chorister or a comprimario, his voice is way too good. For a specialist in popular canzoni, his style and technique seem definitely too refined. A pseudonym? Or somebody who did a completely different job (a doctor, a lawyer...), and had no time for a career in music, thus singing on records only?
Many thanks to Armin Mairhofer for the two Tosti recordings!