My guess is a powder coat.
There's a Rustoleum dark gray metallic color that I used for the trailer hitch that is close, just slightly darker and more gloss.
Zoom in on the left edge of this.
Yeah, the thinness made me question whether it was a coating or not. I don't know if you have access to this paint. I use it on my b-b-q grills. There is an equal heat rated primer that I use with it.