Yesterday:
Overlaid:
No way would me fiddling for a few seconds in MS Word produce the exact same results as a 30-year-old typewritten document.
On these documents the "age spots" are more consistent with putting dirt and dust on the copy glass than the diffuse age spots that you would see with yellowed aged paper.
I dug out my old Army records 1967-1974 and looked at several documents and the 4 is definitely not the same as the 4 produced on typewriters of that era.