Some sort of basic steering lock was my first thought given its location and solidity.
I thought that initially but when I got it apart I found a type of rachet wheel which I presume acted on a rod or something passing through the lower hole. You can see it in the last pic. Also it is just a pull knob with no key so not much of a lock.
I think I prefer the 'ejector seat button' especially when I am trying to get out
