Stephen Jay Gould's "Phyletic Size Decrease in Hershey Bars", in "Hen's teeth and horse's toes" at https://archive.org/details/hensteethhorsest00step/page/314/... shows the size trend from the 2.0 ounces of 1960 to the the 1.2 ounce of 1980, when it was published.
Implied by the Devil Dog mentioned later in the essay:
> And I will say this for the good folks in Hershey, Pa. It’s still the same damned good chocolate, what’s left of it. A replacement of whole by broken almonds 1s the only compromise with quality I’ve noticed, while I shudder to think what the “‘creme”’ inside a Devil Dog is made of these days.