A new exhibit at the Harley-Davidson Museum is proof the company is about much more than its classic motorcycles.

An all-leather motorcycle made in Japan, rarely seen prototype bikes and a rocket engine that powered drone missiles during the Vietnam War are just a few of the items the company has dug out of its archive for “Collection X- Weird, Wild Wonders of the Harley-Davidson Museum.”

The museum’s senior curator, Kristen Jones, said certain items were chosen to tell particular stories when the museum opened nearly three years ago. But many got left in storage, only to be glimpsed by museum goers on special behind-the-scenes tours.

It’s from those tours that curators got the idea to put together the new exhibit, said Jim Fricke, curatorial director.

“You see the look on people’s faces when you let them into the climate-controlled storage area and we begin to pull out this treasure,” he said. “So we decided to play off the kind of mystery embodied in the kind of secret storehouse. That’s where the theme came from.”

The exhibit, which runs through Aug. 21, includes a 1920s leather aviator’s facemask, a tiered “trophy cake” that displays racing trophies from the early 1900s and handmade kidney belts that riders wore through the years.

“There are a lot of different chapters, and there are chapters that aren’t as well-known as others,” said museum vice president Bill Davidson, the great-grandson of Harley-Davidson Motor Co. co-founder William A. Davidson, describing the history of the company where he’s worked most of his life. He said just talking about the exhibit gives him goose bumps.

The vehicles on display highlight a lesser-known side of the popular motorcycle maker.

There’s the all-leather motorcycle, a 3/4-scale replica that it took 20 craftspeople from a Japanese company specializing in leather products more than two years to complete. There’s the Rikuo model, the first motorcycle manufactured in Japan, which was made by a company that licensed the tooling and design of a Harley.

There’s also a prototype of a liquid-cooled motor-cross bike from 1978 when the company considered getting into that market, and “Project K,” an experimental, three-wheel vehicle from the mid-1980s that was a cross between a motorcycle and a car powered by a Harley engine.

Harley-Davidson has 500 vehicles in its archive, as well as 150,000 photos and negatives, 7,000 pieces of clothing and accessories, and loads of marketing literature, manuals, business documents and personal mementos like journals and diaries.

The archive dates back to when the company started in 1903.

Davidson said walking through the exhibit brought back many memories.

“It’s very rewarding for me to see these and remember back when we were actually testing them, riding them,” he said of the vehicles on display. “Very exciting.”