There is two types of laser diode. They're electronically diferent. New PS2s can use both (V4 or newer) older PS2s have a lot of trouble using the new laser diode. Original lasers which have the new diode have a yellow ring on the lens. Old ones the ring is white. This doesn't apply to refurbished lasers for obvious reasons (chinese people have no reason to bother with the color of the ring as the lens are the same regardless of the color of the ring.)
400C lasers with orange flexible board do have the old laser. All 400B lasers have the old laser as well.
I hope this was informative.
Ah I forgot to mention that using a 400C in a V3 will cause your DVD ribbon cable to bend and break...
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)