For sale: This 1937 Yellowstone tour bus is the ultimate party cruiser

Mark your calendars for Oct. 5, when this ultimate one-of-a-kind party bus hits the auction block.

The 14-passenger White 706 bus was built by the White Co. out of Cleveland and bodied by Cleveland coach builders Bender as part of the last generation of open-air tour buses for the Yellowstone Park Transportation Co. According to the National Park Service, 98 Model 706s of various years were put to use in the park, the largest number of National Park buses operating anywhere, and a few were in operation as recently as the early 1970s.

Designed by famed Russian-born automotive stylist Count Alexis de Sakhnoffsky, the buses were originally equipped with a six-cylinder engine on an overbuilt 190-inch wheelbase chassis. Here's what the NPS says about the 1936 version of the bus:

his vehicle, like the Model 614, has a 6-cylinder engine, although a flathead motor (the mainstay of most auto manufacturers before World War II), as opposed to the more sophisticated and expensive overhead valve engine of the Model 614. It also has a noticeably different body style (most evident by the windshield and front end). Also present on the driver's side is a semaphore turn signal, a Wyoming requirement for buses operating in that state. A divided storage compartment, or "blanket chest," is located behind the rear seat and was used to store blankets for passengers' comfort.

The version to be auctioned substitutes a 300-cubic-inch Ford inline-six engine and automatic transmission. It's also got power steering, a 1995 Ford F450 master cylinder with power brake booster, 12-volt electrical system and electric fuel pump to make it more adaptable to modern driving requirements. And don't forget the removable canvas roof!

Sotheby's expects the bus, which is being auctioned in Hershey, Pa., to fetch between $30,000 and $40,000. It comes with period photographs of other Yellowstone buses.