A bus friend sent me a link to the Crown Bus Company–here’s some of the info on that bus:

Crown Coach Corporation was California’s specialty builder of school buses and other specialty coaches. Crown called their masterpiece the Crown Supercoach.

Crown completed their first bus in 1932. An all metal body with safety glass windows. It was rectangular in appearance. The cost of such units was very high during the Depression time, so in 1935 Crown brought out some school bus bodies on a commercial truck chassis These were called Metropolitans or Metros for short. It had simple bodies on a commercial truck chassis.
The same year Crown put out a larger and stronger model it was manufactured more than the 1932 model, now known as the Crown Supercoach, it had air brakes and carried 76 elementary students and 67 high school students.

Crown made the first underfloor engine school bus in 1937. The seating capacity increased to 79 students it was the largest school bus of that time. The engine was moved to the rear in 1940, with altered body work allowing two emergency exits and more headroom. In 1947, the school buses changed back to underfloor engines. In 1950 Crown changed some body features to a more rounded shape which adds extra strength, the resulting appearance was almost unchanged except for window sizes for the next forty years.

All Crown vehicles had gasoline engines until 1954 when the engines changed to diesel engines.