leIG - Leichtes Infanteriegeschütz.
That's fielded from T2, the medic truck.
Usually T0 is a HQ that doesn't build combat units.
T1 is the lowest combat tier (The HQ for Oberkommando)
T2 is the medic truck
T3 is the repair truck
T4 is the Flak truck.
That's the way our guides use it and it would be nice if you guys on CoH2.org could use a similar terminology just to reduce confusion. Thanks 
Edit:
If you want to look up units - http://www.coh2.org/guides/18815/oberkommando-west-unit-guide
and sory im used to coh1 and the hq is t0 there and then the next tech building was t1, next one t2 etc, why did you guys change that ?
hm you may seem to be right about the infanterie geschütz, but i got hitted several time from far far away and these shoots even penetraded my tanks/vehicles, but since it fires 7,5mm shells it might be able too..