The extremely heavy-duty Mercedes-Benz O 10000 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 case of double-deckers.

Though heavy in weight at 12 tons, it could still run at 65 km/hr. Only less than 250 were made and several were purchased by 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 see this mobile post office.