The problem is the amount of variations of the T5, if you counted every possible combo it would likely be well over 1,000 different specs and that isn't even counting the T5 Z, or Z spec as the us call it.
There is a way to tell the box apart externally whether it is a WC or NWC, but only if you can see the front of the box hidden by the bell housing, the bearing race closest to the input shaft is indented on a WC and flush on a NWC.
WC and NWC have NOTHING to do with power potential either, WC is world class, simply meaning same box(spec) used all over the world, NWC meaning variants of base box used all over the world.
Later T5's actually had electronic speedo drive, one is on it's way, with the addition of a sleeve to make up for a 6mm difference in diameter will fit cossie T5's.
There is a multitude of different materials used, and to make matters worse, what is supposed to be in your cossie box isn't necessarily what's really is in it!!
tabetha