Thanks for the lock Gerd. I'm not exactly sure as to what you are looking for, but I just came across these two sentences, and thought they might be applicable:
"The first truck with the name Magirus was built in September 1916. It was a 3 tonner, with a 4 cylinder engine of 6082 cc, which carried 40 HP out at 1100 rpm."
Perhaps the puzzle vehicle is the first Magirus truck, and thus a cause for celebration.