Well, if it was a technical manual for a Spirit Duplicator, it would make sense, as "Ditto" was a brand of Spirit duplicator. Many publications over the years in Science Fiction Fandom were done using "Ditto" machines, which lead to a vast lore of filks, in-jokes and even a play about the "Enchanted Duplicator", since it duplicates "Spirits"!

And I bet you never wanted to know all that. Suffer. :-)