The extremely heavy-duty Mercedes-Benz O10000 was a replacement for the L8500 in 1935. It was the largest bus from the Mercedes-Benz stable that could offer 50 passenger seats on single deck buses and up to 80 passenger seats in the case of a double-deckers.

Though it was heavy in weight at 12 tons, it could do about 65 km/hr. Only less than 250 were made and most were purchased by the Post Offices in Germany and then Austria, where they were used as mobile post offices.

If one visits the Stuttgart musuem of Mercedes-Benz one can witness one of such mobile post office.