Just another microbus stuffed with equipment.
The pump is powered by a modified VW air-cooled flat-four. It can be removed from the vehicle and moved closer to the water source. A handle at each corner makes it easier to carry.
Plenty of room for fittings and hoses in th rear.
UPDATE March 24, 2023: As reported in Jalopnik and TheDrive, sadly, this wonderful collection was sold off in 2019 after the museum's closure a year earlier. As of this update, photos of all the vehicles can be found in Oldbug.com for those of you interested.