Thanks again, everybody.
The tankette is a conversion of the 1:72 Emhar kit of the German A7V WW1 tank.
Just did this because I like the A7V tank, but wanted it to look different after having building a number of them in camouflage.
Just added bits from the bits box, I guess you are right, the main weapon is a smoke screen mortar.
I didn't plan it to be used in a game (and it might not be useful as the original tankettes were not useful)
But I guess it would work in any near future city fight scenario.