How do I find the manufacture date of a PSP ?

I have recently found a PSP, that has an american packaging, and a Japanese PSP.........that is, the packaging is all American, PSP-1001K booklets, Region 1, etc, USA box, etc...but the actual PSP is PSP-1000 !!! Now obviously the thing has been re-packaged......I found just one small scratch on one corner of the LCD, otherwise it looked clean,..the UMD seemed to be unused (no scratches)...also the firmware is 2.70, but I wont trust this cuz maybe its an old PSP which is just upgraded.......

I just want to find the manufacturing date (not the exact date, just a month or so wil do) of the PSP itself (not the packaging), to make sure that its not old/refurbished.........so can i do this, just be examining the PSP itself ?? I know the serial number and the code written on the long thin bar code at the bottom part of the PSP....maybe these are helpful.......

ok, i have just been told that there have not been any PSPs released so far, that come factory installed with 2.70...that is, every 2.70 out now anywhere, is actually some PSP that has been upgraded to a 2.70.......is this true ??

Sony does what ever it takes to upgrade the firmwares and release them to the public. They hate the fact of people being able to run emulation and loaders.