Strange objects within doors

“You can talk to someone without opening the door; it’s called a speakeasy.’” The question “What is the purpose of this little door in the door?” was answered by Reddit user 3rdCoastTxn.

“When we moved in, my girlfriend took it with us. How do you describe this? It is perhaps the most bizarre thing we have ever seen.

“It works your abs.”

discovered during a refurbishment. It has a stone at the end and is six inches long. The finish is boring, but a Google image search indicates that it’s a pin. Any suggestions?