PS2 version question

[swifferman]

Does any know at what point in time the PS2 Version 4's were made?
Any help would be appreciated
And can anyone also tell me when they fixed the disc read error program where it blows dust over the lens so you like have to clean it and readjust it?
Thanks

[jonapete2001]

I you have a serial number sticker on your system(on back by expansion bay) you can look up version on this site.
http://www.whitedog.co.uk/ps2-version.shtml

[swifferman]

I you have a serial number sticker on your system(on back by expansion bay) you can look up version on this site.
http://www.whitedog.co.uk/ps2-version.shtml

Thanks
It's a version 4 but what I really wanted to figure out is when it was made?
Or the differences between the ps2 versions?
Ty!

[peasantlover]

version 4 = sucks 2.7% less than version 3.