That truck is a bit of a puzzle.
I see almost no exhaust smoke on the bin. So likely the bin was put on shortly before it was retired. Maybe this bin was to re-purpose the truck for a second life, for short-haul field harvest or something. The bin couldn't be nearly as old as the truck, the lumber is hardly weathered and there are no rust stains of the bin structure.
And the bin is lightweight construction in contrast to the 8 drive wheels below it. I wonder if it started out as a dump truck or similar.
Maybe its just parked, not retired, because it's only used a week or so per year for harvest?
What would that V-bottom bin be used for?