Repros are aluminum. Originals were aluminum 68-76
They originally were treated in a "Bright Dip" protective surface treatment. Like an anodizing but not technically anodizing. The Bright Dip actually makes the part little more shiny looking..
Steve, thanks for this info. Do you know if there is a way to duplicate this coating as a DIY? Or where to buy "Bright Dip"? Is it actually dipped, or sprayed on?