Can anyone please tell me what these old white 4x4 circles are? What are these?



They are from a box of very old LEGO bricks, circa 1981.
It looks like 3 of Turntable 4 x 4 - Old Type Complete, Perfectly Round which came in 13 different sets from 1963 - 1970.



I'm guessing the one in the middle is either broken or disassembled (if that's possible), and the top of it attached to the bottom of one on the right.