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?

[Arakon]

if it has 10 screws, it's a V3.
if it has 8, it's a v4 or v5.

the messiah works in all PAL models.

[charlie_ps2]

10 screws on the bottom - v3
8 screws - v4

[morteza]

messiah also works with v4 ps2

[modchip12]

Use this guideline http://www.modchip-sbox.com/howtoIdentify.shtml