I've seen this subject addressed, but never cleared, specially for the 2001/2002 engines, because the 2003 engine will be different outside (magnetic bung, and head bleeder screw).
My idea is that all of you that still has this bikes put here your engine numbers, and that way we will figure it out.
I've made a search and based on the numbers that I will show, I have a theory, but is yet to be confirmed.
My bike 2002 FE400E - Nš 4012709 - 401 (FE400) 2 (2002) 709 (serial number)
Edelweiss engine, FE400 doesn't know the year - 4013198 - for me 401-3-198, so I would say it's a 2003 FE400
Dannyboy bike 2003 FC550 - Nš553311 so 553 (FC550) 3 (2003) 311 (serial number)
A friends bike that I thought it was a FX 470 - 2001 but number 4722030, so for me 472 (FX? 470) 2 (2002) 030 (serial)
Pictures of cases that I saw on ebay
the vendor says FC470-01, engine number 472 1 011
the vendor says FC470-02, engine number 472 2 004
This two confirms my theory
I also have seen one casing with 473 1 011, this one I would say it was one 470, maybe this one was the FX not FC ?? from 2001.
I think you all understood my theory, now if you all add your knowledge I'm sure we will come to a conclusion.