Thanks for the link. How can the inking of a ribbon explain the difference between the first "t" in the word "student" compared to the second "t" in that same word? (and the other letters as well?)
If the ribbon has been rewound a number of times, or amateur re-inking has been employed, it will almost certainly never print the same letter exactly the same way ~ not even in the same word.
Someone else can verify the movements on any particular manual typewriter BTW,