10 Screws at base of PS2 Version 1, 2 and 3
USA SCPH 30001 Version 1 = Serial Number begins with U1 Date Code 0D
USA SCPH 30001 Version 2 = Serial Number begins with U0 Date Code 0D
USA SCPH 30001 Version 3 = Serial Number begins with U1 Date Code 1A
USA SCPH 30001 Version 3 = Serial Number begins with U2 Date Code 0D

8 Screws at base of PS2 Version 4,5 and Electrical warning stamped on the bottom
USA SCPH 30001 Version 4 = Serial Number begins with U0
USA SCPH 30001 Version 4 = Serial Number begins with U1
USA SCPH 30001 Version 4 = Serial Number begins with U2
USA SCPH 30001 Version 4 = Serial Number begins with U3
USA SCPH 30001 Version 4 = Serial Number begins with U4
USA SCPH 30001 Version 4 = Serial Number begins with U5
USA SCPH 35001 Version 4 = GT3 Edition

There are 3 Motherboards for the SCPH 30001R, Version 4, 5 and 6 (5 and 6 are the same)
USA SCPH 30001R Version 5 or 6 Motherboard see below to ID
USA SCPH 39001 Version 7

SCPH 50001 / 50010 is a Version 9

If your model # is SCPH-50000, 50001, 50002, 50003 or 50004 AND if you can find DATE CODE 3D as shown below, you have a V10 PS2 main board