Now, where did said tooth come from (other than the late Beatles star's mouth)? Well, it was apparently given to a gal named Dorothy Jarlett by Lennon himself. She worked as a housekeeper for Lennon and had a warm relationship with him, one that merited the gift of his tooth, apparently.
"She was very close with John, and one day whilst chatting in the kitchen, John gave my mother the tooth (he had been to the dentist to have it removed that day) and suggested giving it to my sister as a souvenir, as she was a huge Beatles fan," her son Barry said (via CNN). "It has been in the family ever since."
The tooth stayed in Jarlettt's family for over 40 years. Now, Dot, as she's called, is 90 and decided it was time to part with the tooth.
Apparently the tooth is too sensitive for DNA testing, but there's no real doubt about its authenticity, since it came from Jarlett herself.
See more pictures of John Lennon's memorial here: