I googled a bit, and it seems I was correct (See here:
http://talk.maemo.org/showpost.php?p...8&postcount=20 ). The same command should show you the lock code on the N770.

In case you're not familiar with the shell, quick pointers. The above command has to be run as root. (As far as I know, "sudo gainroot" should work, but I am not sure how to elevate yourself to root on the N770, someone else who actually has one will know the exact command if you don't - or you can google for it.)

Anyway, enter these commands (copied directly from linked post, but it's basically what I would've said):
Explanation, if someone wants to understand that set of commands:
"/dev/mtd1" is a 'virtual' file, it really points to the part of the N770's storage that contains the 'CAL area', which on these Nokia devices is where they store some of the more critical settings. "grep" takes the input given to it (in this case /dev/mtd1), and filters out all the lines except those that match a given string (or regular expression) - in this case "lock_code". The "-A13" option tells grep to display 13 lines after the one that has the actual matched string, since for whatever reason the lock code is 13 lines below the actual bit of text saying "lock_code". The | takes the output of the preceding command, and uses it as the input of the next command. "tail" just prints the last X lines the input, where you specify X with "-X". So "tail -1" prints the last line. This is just to clean up the output, so you don't have 13+ lines of junk. (Also, on the N900, without the tail bit, you'll see that there are two "lock_code" sections. The default 12345 lock code one, and the one that's actually set on the device.

Anyway, hope this helped.