In Checklist of Suspicious Features, Jacqueline A. Joseph, Certified Document Examiner and handwriting expert witness writes:
If you have a suspicious document or handwriting or typewriting, these clues should alert you to the need for a document examiner:
The paper, ink, mode of production or other feature of the document may not have existed at the time the document purports to have been executed or may not have been available in the place where the document originated. An example of that last point would be a computer-generated and printed document from a place where computers were not available until more recently.