The IOToolkit software can be used to send commands to the 1586A to reconfigure the serial number. Click in the link below to install the IOToolkit software
Connect the USB cable between the 1586A (see picture below) and computer.
Select the correspondent port in the IOToolKit software for the USB cable, and make sure the baud rate is set to 9600 in the 1586A and IOToolKit software.
After the IOToolKit is setup to send commands proceed to send the following commands:
WIZARD ELBERETH (type this command as written/no colons or any other character)
SYST:CONF:SNUM <type the 8-digit serial number>
SYST:CONF:SNUM? (Send this command to verify the serial number was recorded)