FWIW, Lightnin' Hopkins was overdriving his amps back in the late 40s, and I doubt he was the first.
Agree. The P-90 (from 1946) is a rather hot pickup, and even the metal cover version from about 1940 is hot too. Even the last prewar bar pickup is on the hot side.
I'd say 50% of the pickups from the mid 30's and onwards would push at least 50% of the amps made for music instruments into overdrive if you played them at 50% volume
There are good prewar overdrive/fuzz stories too, like Charlie Christian playing an ES-150 into a EH-150 on a late night jam sesssion.
Accidentally plugging into the mic channel, he got this mean fuzz. Don't know where I read it, but I think he unplugged it fast only to have someone responding something like 'whatever you did, do it again' or 'plug it back in' or something. Any guitarist playing such gigs or jams in crowded bars (with a drum kit) must have turned up the volume to 11 or used the mic channel more than once back then. Stories like that sound more likely to be true than slashed cones. After a few pints, plugging into the right (or wrong) channel can be quite a challenge