The SWDb entry of La taglia è tua … l’uomo l’ammazzo io credits Fabrizio Gianni with the part of Fernando and Gustavo Re with the role of “Specs” (aka the “Professor”). I am, however, quite sure that Re plays Fernando – but unsure about Gianni’s part. The IMDb lists the “Professor” in La taglia è tua … as his only acting credit, and apparently he co-wrote the screenplay. Information about Gianni is hard to find: reportedly, he worked as Sergio Leone’s assistant on Il buono, il brutto, il cattivo, left the movie business in the 1970s, and became a fashion photographer (cf. The Scotsman and The Falkirk Herald; in his biography on Leone, Christopher Frayling doesn’t mention him in the main text, but lists him in the appendix as “director’s assistant” on Il buono …, whereas the movie’s [English] title sequence identifies him and Giancarlo Santi as “assistant directors”). It would be interesting to find out a little more about this rather enigmatic man – first and foremost whether he played “Specs” or not.