Kerning: the smoking gun?

Once again, a disclaimer: I am not a professional typographical analyst. I'm an amateur. I might be doing something totally wrong here. What I have found might have a perfectly innocent explanation.

Nevertheless, here it is.

The surest evidence for kerning would be to find two sets of four letters in the same document, with the pattern "abcd" and "acbd." Line up their initial letters. If there were no kerning, the terminal letters should line up also. If the pairs "bc" and "cb" were kerned differently, the two quads would have different lengths.

I wrote a program to search the memos for quads that fit this pattern, and there is exactly one: the word "from" and the last four letters of "perform." Happily, both are in the same memo, eliminating any possible differences from memo to memo.

Here are the two quads, top to bottom. The blue lines are vertical. The letter "f" is lined up.

I report, you decide.

Update: After doing a bit more research, I'm unconvinced that the documents are truly kerned. On the other hand, I'm unconvinced that they're not kerned, too. I'm leaving this up in the hopes that people who know more than I can sort it out.

Update 2: The more I look into this, the more I come to the conclusion that these documents do not exhibit true kerning. But they do show clear signs of "pseudo-kerning", where certain glyphs extend beyond their bounding boxes. You can see this in word by typing the pair "fW" and witnessing how the upper right part of the F and the upper left part of the W actually intersect. I don't know if any typewriters from the 1970s had this feature, but I kind of doubt it.