The finish really gained popularity with the "Spirit of Saint Louis" airplane.
Honestly, I don't have time to perfect something like this for the Q right now. It would definitely be a winter time project when I can't do much outdoors.
Here's a car like the one where I first saw the finish on engine components.

Here's what a Q valve cover would like with an engine turn finish. I would really need a lot of practice to pull off that type of finish. I decided to snap a picture before I erase it to go with a brushed aluminum look.

