Here are some pics of both of my old turbos (W11 T25 and GTiR T28)
One main way of telling is by size, T25 is a bit smaller.
Turbine Housings:
Compressor side, GTiR T28's have two bolt inlets
Outlet side both have 3 bolt outlets, but they are angled differntly
OT: Tried the Eibach's handled pretty good but just a bit too stiff and low