Firma e data in basso a destra:

Noteː Even if it is titled portrait of 'Ettore' Panzacchi, who I did not find his name anywhere, it is more probably about Enrico Panzacchi, Italian Italian poet, art critic and music critic, these are my reasons why I decided to put him instead, at least for nowː

• The theory is somewhat helped by the vague 'Panzacchi' in the dedication.
• Enrico Panzacchi was along many things and art critic, so he could be that they knew each others, and were friends as well. 'Al mio buon' (To my dear), is not written to a stranger, we can say quite surely that this person knew Corcos well and viceversa.
• Also you can see his name cited in the epistolary the artist's wife (Emma) had with Giovanni Pascoli. 1
• The images depicting Enrico Panzacchi seems to match quite well the subject depicted here. 2
• Panzacchi during this time teached at the Accademia di belle arti di Bologna, where the painting is currently located.
• Corcos made two portraits of Carducci (1892) who teached at Bologna, at a different university of Panzacchi. But Panzacchi, and Carducci where close friends, and Carducci could have presented Corcos to Panzacchi if he had not yet know him before.

• Ottocento. L'arte in Italia tra Hayez e Segantini, 040 
• Ottocento. L'arte in Italia tra Hayez e Segantini, p. 331