rev a-c is like calling the car a series one and a rev d-e is a series two.
rev a-c 1999-2002 i think ( the grill is rounder)
rev d-e 2003 (squarer grille)
Just to clarify:
Revision A = 1999
Rev B = 2000
Rev C = 2001
Rev D = 2002
Rev E = 2003
I have an MY02 RX and mine has the honeycomb style grill.
Hope that helps.
Also as far as I'm aware, I don't know of any aftermarket grills for the Rev D-E models, only Rev's A-C