At long last, it seems that Del Frate's 1876 manual has been digitised:
https://books.google.com.au/books?id=GZjNfgA8JdMC
Of course, a great English translation has existed since 2011 thanks to Chris Holzman, however it's always nice to have access to a manual's original language. Google's scan is unfortunately missing the plates (another reason to go get Holzman's translation).