Whereas chief rival BMW builds bikes as a (substantial) sideline, Mercedes-Benz, beyond boasting the largest luxury car model range of any German brand, turns substantial revenue courtesy of its truck and bus business.No surprise then that the company’s most revered truck product, the go-anywhere-in-any-weather Unimog, was thrown a birthday celebration in Germany last week as its turned 60. MOON BUGGY BIRTHDAYAlthough celebrations centred around its unmatched heritage as the world’s most trusted civilian heavy duty off-road utility vehicle, Unimog product planners also revealed a concept truck at Mercedes-Benz’s Worth assembly plant. The new concept truck is meant to give faithful supporters of the legendary ‘Mog nameplate a glimpse into what future holds for Mercedes-Benz's most hardcore line of 4x4 vehicles.Featuring radical open-cab styling (paying homage to the original U411 baby ‘Mogs), the concept truck (with its oversized wheels featuring chrome overlays, exposed chassis and red coil springs) rides on a traditional U5000 platform.Boasting portal-axle drive to all four wheels, nearly 500mm worth of ground clearance and class-leading individual wheel articulation, its ability to traverse broken terrain is peerless.The styling is (very) elaborate. In fact, it it looks like a moon buggy for the European space agency, with the green cab section finished in an al most Shrek-like hue. It's hard to see how some of the detailing could be incorporated into the current Unimog range, but Mercedes-Benz says this concept truck does point towards future styling for the Unimog range...As a birthday treat though, it’s an excellently executed homage to all things great about the Unimog.