Funny I came across a mac color classic with this diode on u8 as well. Someone installed a pin header for a battery pack on the board.The board is labeled as 823-0367-c. I have found only one picture on the internet that is identical. By the way, these have a diode between pins 7 and 1 on U8 that i cannot see on other boards, and does not show on schematics. Any idea of which would be its purpose?