The 1938 O 10000, a massive and quirky bus, offers a unique glimpse into post-war transportation. Mercedes-Benz explains that by the 1960s, the O 10000 was converted into a mobile post office.

Stacey Kelly, employee of the U.S. Postal Service, gets a bag ready to pick up the day's mail in the mobile post office van she operates from the Gas City parking lot at 6150 S. Kolb Road. The van ...