The bones, deposited by a mystery donor in a cardboard box with a message saying they had been excavated in the 80s, won the Most Unusual Item category at the Association of Charity Shops' annual awards.
The remains were taken to a St Barnabas Hospice shop, where they were transferred to a central collecting unit. They lay untouched for a fortnight until a volunteer bric-a-brac sorter opened the box and made the grisly discovery.
"We think they had been left in someone's house or garden when they moved," said Caroline Grosse, retail area supervisor for St Barnabas Hospice. Grosse donated the skeleton to The Collection, a museum in Lincoln, after a friend who works there authenticated it.
"Charities are used to receiving all sorts of weird things, but you really don't expect a skeleton," said David Moir, head of policy and public affairs at the Association of Charity Shops.