Don't know for sure, but it looks like its been blasted, maybe vapour blasted or maybe bead blasted (silicone beads give a finish that looks like that, and can also give a satin look by smoothing out the surface imperfections).
BTW, just made a video just for you...
https://youtu.be/USUq-2uP694
BTW, just made a video just for you...
https://youtu.be/USUq-2uP694