On the main screen type

*#06# for checking the IMEI (International Mobile Equipment Identity).
*#7780# reset to factory settings.
*#67705646# This will clear the LCD display(operator logo).
*#0000# To view software version.
*#2820# Bluetooth device address.
*#746025625# Sim clock allowed status.

*#62209526# – Display the MAC address of the WLAN adapter. This is available only in the newer devices that supports WLAN like N80

#pw+1234567890+1# Shows if sim have restrictions.

*#92702689# – takes you to a secret menu where you may find some of the information below:
1. Displays Serial Number.
2. Displays the Month and Year of Manufacture
3. Displays (if there) the date where the phone was purchased (MMYY)
4. Displays the date of the last repair – if found (0000)
5. Shows life timer of phone (time passes since last start)