The gold writing is to the right of the right trigger ( looking at the psp from the back).
Here is something i slapped together in MSPaint to give you an idea of it's location.
http://img156.imageshack.us/img156/3228/pspgos5.png
From what i can make out it seems to say IC6001, though i can't be certain but i can be certain their isn't a number 3. Oh and i have to turn my PSP upside down to read it.
I tried to use those 2 programs that were linked but they won't properly probably because they can't be used on 2.70+ as said by the website they come from.