how to tell what ver. of ps2 i have

[maddog_rules]

gretz,Serpent & charlie_ps2
first one is SCPH-30001 date code 1A -U162xxxx PT1162xxxxx
the second one is as stated below
SCPH-30001 date code 1A -U307XXXX
PT1307xxxxx
the date code is as stated is there another way to determine
with out opening it up
went to the link posted no screws in bay opening on 1st one
and it has 10 screws
the 2nd one has 8 screws and 2 screws visible in the bay opening
also on the link it noted magic3 wont go on the first release
at launch 010 bios well how do i check the bios version
on my first model
well please advise on both to confirm which mod i'll need to get
also what makes messiah2 better than magic 3
need all the info on both chips please