Identify what version PS2 you have

The version 1, 2 and 3 PlayStation 2 all have 10 screws on the bottom of the unit.

SCPH30001 v1 = Serial# begins U1
SCPH30001 v2 = Serial# begins U0
SCPH30001 v3 = Serial# begins U1 Date 1A
SCPH30001 v3 = Serial# begins U2 Date 0D

The versions 4 through 10 PlayStation 2 all have 8 screws on the bottom of the unit.

The 4 and 5 also have the electrical warning stamped on the bottom of the PS2 case.

SCPH 30001 v4 = Serial# begins with U0
SCPH 30001 v4 = Serial# begins with U1
SCPH 30001 v4 = Serial# begins with U2
SCPH 30001 v4 = Serial# begins with U3
SCPH 30001 v4 = Serial# begins with U4
SCPH 30001 v4 = Serial# begins with U5
SCPH 35001 v4 = GT3 Edition

There are 3 different motherboards for the
SCPH30001R - Version 4, 5 and 6
SCPH30001R v5 or v6 Motherboard
SCPH39001 v7

SCPH50001 v9

SCPH50010 v10