What Kind of PSP's are eligible for Custom Firmware?

I'm not entirely sure on what kind of PSP I have (I'm sure it's not a GO) or the firmware already on it (I can find out easily) The only piece of info I can give is the barcode number on the bottom of the system, It either begins with AB02 or A802, I know it won't be easy to help with so little info, but if you could still try, I would appreciate it.