It's unknown whether the pontiff ever rode the custom 2013 Dyna Super Glide that was a gift from Willie Davidson, a retired Harley-Davidson designer and grandson of the company's co-founder.
The pope's hog is expected to fetch between 12,000 and 15,000 euros ($16,000-$20,000) when it goes under the hammer Thursday at the Grand Palais, said Ben Walker, head of collector motorcycles at the auction house Bonhams, which is organizing the sale.
Money from the sale will be donated to the Rome-based charity Caritas Roma, which runs a soup kitchen and a hostel for the homeless in the eternal city.
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