A Harpoon Trakk.
The unpainted work in progress can be seen here!
The glyph on the front comes from the Fantasy Orc shield sprue.
The harpoon and gunner were taken from the gorkamorka harpoon trakk.
The driver had his head removed and a new one added from the ork boyz plastic sprue.
The armoured skirts are made from 0.5mm plastic card. More details on how to do this conversion.