PS2 Version 3 or 4?

[Zerotex]

I have a playstation 2, but i don't know its version. A friend of mine tell me that is a version 3 because the serial number and model (SCPH30001 U2.... Data Code: 0D). Otherwise some rumors said me if it has serial number U2 starting and data code 0D, it's version 4.
What's the trues about it? My Playstation is version 3 or 4?
Messiah modchip only works in US V4 console or works in PAL console too?