A member in our forums, ThatDude, has shown the way to tell what version firmware the PSP has before you buy it. The technique is simple and has been verified by many people to be accurate.

On the back of the PSP box by the barcodes, there will be either an ‘A’, ‘B’, or nothing at all located below “120V”. If you do not have a letter that means it was purchased sometime near the US release. Having the letter ‘A’ means that the firmware is a 1.50, and seeing a letter ‘B’ there means 1.51. Now you won’t have to open the box to know your firmware, and most people are willing to find you a PSP box with the letter ‘A’ or no letter at all.

This is still an ongoing research project my members in our forums. If you would like to read more about it, or help to add some new findings you can discuss it in our forums

g laisser la version anglaise pour l´info complète parce que je ne traduirai que ceci

le numéro de serie qui détermine la version votre PSP est en faite une lettre
A pour le 1.50
B pour le 1.51
c pour le 1.52
pas de lettre pour la 1.0(à vérifier)

voici le lien pour les photos
http://www.pspupdates.com/
parcourez le site sur la première page(je vais quand même pas le faire pour vous!)