*#0000#

Command code to display software version information in Nokia phones. The first line is the version number, the second line is the date the sofware was done, the third line is the phone type, and the fourth line is a copyright notice.

My 7110e displays:

V 04.84
07-04-00
NSE-5
(c) NMP.

That one doesn't work for every phone, I'm afraid. For example, with my 8110i the code

*#8110#

does the aforementioned thing. Except without the copyright notice.

You use different codes for different cellular technologies. For example:

*#9999#

works on TDMA phones and some CDMA phones.

*#0000#

works for GSM phones.

*#837#

works for the newer CDMA phones.