I checked some of the devnotes and couldn't find the pinout in any of the relevant models -- Quadra 700, Centris/Quadra 610/650/800, LC 475/Quadra 605.
It looks like Macs as early as the LC had the socket, and unfortunately the LC's devnote seems to be impossible to find. I'd wager a guess that the pinout is in the LC devnote. The LC is too new to be in Guide to the Macintosh Family Hardware. It's in Apple's list at the link above, but the link unfortunately points to the LC 475 note instead. If anyone ever finds the original LC dev note, I'd be very interested in adding it to my collection!
It looks like Macs as early as the LC had the socket, and unfortunately the LC's devnote seems to be impossible to find. I'd wager a guess that the pinout is in the LC devnote. The LC is too new to be in Guide to the Macintosh Family Hardware. It's in Apple's list at the link above, but the link unfortunately points to the LC 475 note instead. If anyone ever finds the original LC dev note, I'd be very interested in adding it to my collection!