Considering what was going on in San Francisco in the late 1960s, it's a wonder that there weren't more issues with machine/mechanical doubling. The Haight-Ashbury district wasn't far away from the mint.
Machine Doubling was very common on the 1968-1972 cents. The 1969-S big DDO has a very large number of MD on the DDO:
Note the yellow arrows. You can see it is a doubled, but the arrows are showing MD. Machine Doubling is alteration of the coin post strike. Well this can happen also on doubled die, the same way it happens on normal dies.