Retrieving your OS X Server’s serial number if you’ve lost it.
To do this on a running system:
1. Log in with an admin account.
2. Open Terminal.
3. Type sudo cat /etc/systemserialnumbers/xsvr
Your OS X Server’s serial number and the registered name and organization should be displayed.
If you’re retrieving from backups, get the xsvr file from /etc/systemserialnumbers to retrieve the serial number.