I got my pi-top CEED today — and thankfully it came with the PROTO board and a nice printed label naming the pins (see photo below).
Now, I assume that the label is meant to go over the GPIO pins (see other image), at last it matches nicely. However, (to me) the question remains, what the top left pin actually is: According to the label it could either be pin 39 (GND) or pin 2 (5V PWR).
Where can I find some documentation that explains which on it is. In the end, mixing up the 5V power with ground can destroy stuff…
The 40 pin connector on the top of the PROTO board copies exactly the 40 pins of the Raspberry Pi, including the orientation. On the left side is pin 1 (below) and pin 2 (above).