Yours were the only significant claims in this discussion. A couple of factual claims pertinent to the topic. Those claims, evidently based upon generalizations of your own personal experience are thoroughly rebutted by linked and abstracted citations of typewriter history and databases.
What you are talking about is really old news and no longer worth discussing. There's been a full exposition of typewriter history, rubber stamp history, electric typewriter history, computer history, laser printing history, and a whole host of other items.
We've had people deny folks had electric typewriters earlier than 1961, and those who denied manuals were used later than 1959. Some have argued that rubber stamps simply can't produce letters as crisp, or smudgy, as those in Obama's COLB/LF.
Others rejected the idea that anyone could have mastered manual typewriter operations well enough to produce anything but clumsy, smeary work.
Etc.
You think of it, they've claimed it.
My experience in the matter covers the technology from the early 1960s right up to the present day with THOUSANDS of difference pieces of equipment that might have been involved in producing or forging these documents.
So, not being able to fight the facts you are taking on the writer ~ ?
I think you've lost the debate before you can even begin. Now, for a final reference for you ~ a piece on how to make a rubber stamp-like image using PHOTOSHOP. The comments end in May 2011.
KOINKYDiNK? You be the judge. Try: http://www.laughing-lion-design.com/2007/07/photoshop-tutorial-create-a-rubber-stamp/