What version PS2 do I have !!?

[mud ver.2]

30001, serial U2...

You would think I have a ver 3, but it gets more interesting. My unit has 8 case screws. And the mother board looked identical to my buddy's ver 4.

I am currently using a NEO 2.5 chip with no problems (haven't tested dvd-r backup yet). The NEO 2.5 wasn't supposed to work with ver 3 units. So whats the deal ?

Do I have a ver 4 with a ver 3 serial ? Is my PS2 from outer space ? I'm planning on installing a Magic 3 chip, but obviously the installation method depends on my version of PS2. Any input from you guys would be great.

Thanks.