I'm pretty sure the Q650 and Q800 boards were the same, weren't they?

Also, are you certain that 16.7 MHz oscillator is for the CPU? It could be for some other circuitry. There are usually three or four on an Apple motherboard.

The 64 pin slot is a ROM socket, in case Apple ever decided to release a ROM update, which it never did. The one with the socket populated is probably an older production of the board than the one with it missing.