This is the pump for the front plow. Or at least a pump for a plow. Most newer plows are self-contained, the up-down cylinder assembly also houses the pump and the valves for everything, It's not uncommon for people to just switch to the newer style but leave the old pimp in place. The reservoir on this pump doesn't have enough volume for the dump, them cylinders are huge and take gallons of fluid to fill. Hence the dump tanks usually being half the size of a normal fuel tank.