Resolution

To retrieve Parallels Server Bare Metal license (activation key) information please issue the following command on Parallels Server host in question: 

# prlsrvctl info

It will result in the output alike to given below where 'key' string contains activation key information for current Parallels Server installation:

ID: {ff74a89b-ad9f-4b6b-a3b5-d45ac9780e5c}
Hostname: 127.0.0.1
Version: Server 3.0.5403.413162
OS: Linux Version 2.6.18-028stab062.6
VM home: /var/parallels
Memory limit: auto
Minimal security level: normal
Manage settings for new users: deny
License: state='valid' name='Administrator' company='Parallels' key='3XTP2N-7KW74K-T8JB9F-8TM3P1-P3Q1Q0'

Hardware info:

hdd  ATA ST3250620AS                          '/dev/sda'
hdd-part  Linux                                    '/dev/sda1'
hdd-part                                           '/dev/sda2'
cdrom  TSSTcorpCD/DVDW SH-S183                  '/dev/scd0'
net  eth0                                     'eth0'
net  vnic0                                    'vnic0'
net  vnic1                                    'vnic1'
serial  /dev/ttyS0                               '/dev/ttyS0'
parallel  /dev/lp0                                 '/dev/lp0'