What is this 2x4 brick with a clear bottom, a small hole at each end and a 6 brick high pole? It is a 2x4 with a clear bottom a small hole at each end and it is smooth on top with a 6 high pole coming out.

The brick has no numbers on it so I'm not sure what it is I have tried searching for it however I can't find it if anyone knows what set this is from that would be great.
It looks like it's 799c800:



This part was used to implement a simple "hand of god" steering system on a bunch of sets in the 70s.