John Rateliff - author of the History of the Hobbit and former TSR employee - talks about his early D&D experiences,...

John Rateliff - author of the History of the Hobbit and former TSR employee - talks about his early D&D experiences, including use of the Caltech Rules aka Warlock on his blog Sacnoth's Scriptorium

https://sacnoths.blogspot.com/2017/05/my-first-edition-players-handbook.html

He mentioned this once previously, back in 2011 in the comments to a post where I asked him about his early D&D experiences:

http://sacnoths.blogspot.com/2011/12/1st-edition.html