[Mk2] [Turbo] telling gearbox's apart

[tops]

is there anyway to tell a rev3 gearbox from a rev2?
my mate has just bought one and has been told it's a rev3 but wants to know if there is a way to tell?

[tops]

i can not beleive that know one can answer this quetion! thought that there was a few guru's on this oc!