Article ID: 13793 
Products
S-Series, firmware 7.11.01.0026 through 7.21.01.0015 
Symptoms
Error message "Unexpected part Number..." is reported as a module boots up. 
The two variations of this message are:    Unexpected part number of the Base Module in Slot 
. Please
    contact Product Support for assistance.          -and-    Unexpected part number of the Option Module (NEMx00) in Slot
    . Please contact Product Support for assistance.The error message may be seen in a serial console session (12453), syslog ('show support', 'show logging buffer'), and/or the Message Log ('show support'). 
Here is an example from the Message Log:Message   3/42   Syslog Message            07.21.01.0015   03/04/2011 15:17:27
    <3> System[1]Unexpected part number of the Base Module in Slot 1. Please
     contact Product Support for assistance.Cause
This condition may be reported for particular S-Series part numbers, identifiable by means of either a 'show support' or 'show system hardware' command. 
For example:S-Series(su)->show system hardware
 
 . . .
 
SLOT HARDWARE INFORMATION
-------------------------
 
   SLOT 1
      Model:                   ST4106-0248
      Part Number:             9404435
      Serial Number:           104956136341
      Vendor ID:               1
      Base MAC Address:        00-1F-45-9D-55-82
      MAC Address Count:       50
      Style:                   Unknown
      Hardware Version:        2
      Firmware Version:        07.21.01.0015
 
 . . .
 
S-Series(su)->The last four digits of the part number (here, "4435") may also be viewed as the first four digits of the 16-digit serial number printed on the top locking tab of a base module. 
The error message is issued because the part number is not yet specifically known to the firmware. 
Solution/Workaround
Upgrade to firmware 7.21.02.0002 or higher.
Release notes state, in the 'Firmware Changes and Enhancements' section:
code:An S system, while booting, may unnecessarily display and log a message similar to "System*1+Unexpected part number of the Base Module in Slot 1. Please contact Product Support for assistance."
 
Pre-upgrade workaround: 
The error message is effectively harmless, because the module will function correctly. The only liability to this condition is that the firmware cannot check for Option Module / Base Module compatibility (13355).