In the old days, proofreading was laborious, like emptying a bathtub of water with a teaspoon.
We listened to a master tape -- essentially perfect material -- and checked the text in our galleys against that. The WT index for five years was a head-splitting exercise is an aim for perfection, this task handed to Brother Xxxxxxx and me.
It incorporated thousands of entries for the newly completed AID TO BIBLE UNDERSTANDING. I cannot recall the outside source of some data sent us, but I'll never forget "Ruffled Grouse" and "serving Jehovah with hardy (sic) purpose." Oh, yeah -- the running head, "Bablyon the Great."