Original Apple, fully tested PowerBook 150 Interconnect Board. It also contains both the internal speaker. This board is used to connect the top half of the machine to the daughter board via the integral interconnect cable. It also has both sockets for the keyboard, display cable and DC/DC converter board.
Note: It also contains the PRAM battery cell but this will no longer hold charge or may have been removed to avoid leakage so settling like date & time, and startup disk will be lost when the power supply is removed.