ok, look at the this gorgeous pair.
Both T1, the older one has the aluminium diff bearing holders, the later one has the moulded plastic version. Both have their merits, but all later cars had keyed parts to allow some kind of fine adjustment.
The earlier car has very light anodising, green/brown, typical of hard anodising, while the later car is much darker and brighter, almost gold.
The carbon on each car is subtly different too, both in shape and layup. It is most noticeable on the rear shock tower and front bumper brace.
The early car is from 2000, the later car is from 2001. Most likely both european kits as the kits destined for the US had white springs to suit their foam tires.