Here you are seeing the Lisa's I/O board.
This card plus into the 1st (front) slot of the motherboard. It contains two VIA chips to controll communications to the Parallel port, the COPS421 controller which in turns connects to the keyboard and mouse and several other lines. Additionally there's a Zilog 8530 SCC (Serial Controller Chip) which drives the two serial ports, a 6504 CPU which shares 1024 bytes of its memory with the Lisa's. This memory is battery backed up and holds the system information (like the PRAM of the Mac.) The 6504 is the floppy disk controller and it talks to the IWM (Integrated Wozniac Machine) floppy controller. The 6504 has its own ROM, and this is called the I/O ROM. When you boot your Lisa you'll see a pair of numbers on the upper right hand side of the screen in the menu bar. The 1st is the 68K ROM version, the 2nd is the I/O ROM version number.
As you can see at the bottom right of the board, there is a 4 pack of NiCAD batteries. One of my I/O boards died because this pack leaked. Older Lisa's that have this (Lisa 2's and 1's not XL's) also have a switch under the batteries. I suppose it's to disconnect the battery from the 6504's PRAM...