On my 1997 Hunter 340, my table is the same design as Jackberry.
It rides up/down and swivels around the tube it is attached to.
At the top of the tube there is a cut-out with a roller attached to it.
There is a nylon 1/4 line attached to the table which goes around the roller that is mounted to the tube. Inside the tube the line is connected to a counter-weight that slides up/down as you lift the table up or down.
This was a Hunter design not after market.
My problem is that the counter-weight is stuck and there is no easy way to get to it.