This youtube video shows a circa 1915 Hammond typewriter in action:
http://www.youtube.com/watch?v=n2htfA9NGCI
Notice what I mean about the way the keys really "ram" the letters into the paper on these old mechanical typewriters, almost to the point where the metal typeface "dents" the paper? Also notice how much more ink the lead typeface leaves on the paper?
The alleged 1918 Ruth/Frazee contract looks nothing like the youtube typewriter's product. Again, I'd bet good money that the Ruth contract is a fraud, and that the typewritten portions were done on a 1950s to 1960s era electric typewriter such as an IBM Selectric. Electric typewriters use a motor/spring system to "push" the key arms upward on to the paper, whereas the old mechanical typewriters rely on the key pressure of the typist- i.e, the harder one presses the key, the bolder and darker the printing becomes.
The dirty "a" on the Ruth contract has the same amount of dirt/smuding in the open space of the letter "A" every time it appears. In a mechanical typewriter, this "clogging" tended to correct itself, as the operator might strike the key harder/softer each time, tending to dislodge the dirt/ink clog.
But in an electric machine, the key strikes the paper with the same "force" every time, since it's being electrically brought up to the paper each time. The "strength" and boldness would be the same if you barely touched the key or if you pounded the key down with a small hammer, as the key itself is merely a switch which is pulsing current to the motor. Make sense?
I am by no means a complete authority/expert on this. I am an attorney, and had a fraud case a couple years ago involving an expert on typewriters/fonts etc. We had lunch/drinks several times during the trial, and I enjoyed hearing about his profession and training. I sent him the link to the Ruth contract, but he has not yet had time to respond.
TBT