So it turns out that I have a bunch of back issues of Great Plains Game Player and its successor, Gamelog, both of them published by Jim Lurvey. Jim's a great guy - I can say that, having known him off and on for nearly 30 years now.
It just so happens that in an early issue of GP2, there's an article by one Gary Gygax, about the relationship between strength and weapons damage and other abilities. Looks like the prototype for the strength tables in Greyhawk. (I understand from a conversation with Jim a couple of years ago that GP2 was where the Thief character class first appeared, too.)
And then there's The Ryth Chronicle - John Van De Graaf's 'zine of campaigns along the Ryth River, "published as a public service by the Yggrdasill papermill" with the first issue appearing in the 4th week of March, 1975, if I've got it correctly. Interesting thing about John's campaign is that he started keeping records from the 3rd week in November of 1974, so his campaign started with the original three booklets sans Greyhawk. As a historical record, this is an amazing snapshot of what gaming was like Way Back Then.
Details to follow.... :)