Again my Sir Andy school of photography is paying off!
Next you need to cover that back woods engineering! If you want the black flat face, mix up a little filler and fill it , and paint it. Or do as I do, use a silver button, and paint it black, I like a profile change, adds a little depth and dimension to the gauge. For this one I needed a silver button, so that is what I did.
In the instructions it says to drill out the silver button. A little tip is the silver button is mounted on a steel rivet. You can gently pry the two apart. Use your fav glue and put it back on. I used Valco HV-350 It will glue about anything to anything, and is paintable if you get messy. Add a dab of glue and hide that screw!
There you go you will not know that screw was there now from the outside.