I found this piece in a yard sale grab bag. What other elements do I need to make it work? I found this piece in a yard sale grab bag. What element(s) do I need to make this element function as it was originally intended?
Technic Turntable Large Type 1 Base (2856). 

It's a Turntable Large Type 1 Top (2855) which is part of Technic Turntable Large Type 1, Complete Assembly (2856c01).