PSP-1000CW = Firmware 1.5?

I know you could tell between 1.5 PSPs and 2.0 on black american versions but I don't know on this..

PSP-1000CW

Most places say 2.0, while every internet auction(on ebay) with this psp serial seems to have 1.5 as the listed firmware.

If it was 2.0, could I downgrade? I read somewhere that your PSP has to have been the old firmware at one time or another to be able to downgrade.

Thanks for the help, I have never downgraded before but I am rather familiar with homebrew.

Crimson

edit: Keep in mind its mostly about the PSP white's hardware and software that I am most interested in

From mi understanding that serial is for the us black 1.50 psp & jap 2.0 white they have the same serials but from different countrys. I personaly downgraded ablack psp without no problem with that serial.
Now mi white psp doesnt have that serial and it was a 2.0