That body style did not come into production until 2005 and ran until 2011 (I think) when the current cab style was released, new Duonic trans, etc)
It is the FG84 and the previous iteration (gray trim at front of cab and two rectangular headlamps) was FG649.
I would presume that a dedicated plow truck would be covered in rust unless it received additional undercoating and/or thorough daily cleanings to neutralise the sand, water, calcium chloride, soduim chloride and/or magnesium chloride used on the roads.