My sources indicate the dial was changed in 1998, production was from 1996, however they also state that Millenniums (obviously from 2000) are seen with both dials (not at the same time!!).
As an earlier model could be sent in for the "upgrade" , which may have been done for some millenniums, the 1998 date is suspect. Of course the factory may have made millenniums in both varieties.
Bottom line the higher iso dial is not a reliable indicator of age and its presence could indicate an older body updated.
If you are adamant you need the 3200 I would suggest asking is the only sure way, it's not as if they need to take it apart to tell you.