Commodore PC 40-III is an upgraded version of PC 30-III. They share the same motherboard, but 40-III has an onboard VGA adapter installed.
The CMOS battery on this motherboard is integrated inside Dallas DS1287 real time clock controller. It can be replaced following these instructions. Without a working battery, the computer will loose its BIOS settings during reset and it will be not possible to boot it correctly.
The mouse port on this machine is to be used with Commodore Amiga mouse, not the PC serial mouse. It should be configured as a normal Microsoft mouse in the OS.