A Mid-December Mystery for You!

Hello again! I'm not sure how much of a mystery this one is, but I had never seen one of these like this until I came across it in our collection.

You might know it right away! Let me know if you do, of course.

This artifact is rather simple, a small wooden circle with a hollow center; it's sort of a donut shape. On one side a hole has been made, and through that hole, a sort of screw apparatus has been inserted. The screw can be moved up and down, as seen below. 

 I’d better keep this short as I don’t want to give too much away.

Do you know what it is? Is it not a mystery to you? Let me know here or on our facebook.
I'll let you know more about it next week!