The Galvanized Steel will rust,
The WW2 era is very stiff and hard to bend
The Aluminum were made when there was a shortage of Copper
The easiest way to tell WWII mounts is to look at the metal slider on the back.
If it has a letter and two numbers that is required by the Government to manufacture for the Government, it is much later as the military didn't adopt that until around the time of Vietnam. The typical ones will look like "D-22" which was the government number for Best Denmark Emblem Company or G-24 for Gemsco and V-21 for Vanguard. The World War II made one don't have any marks on the slider, except sometimes I've seen Wolf Brown put a W-B on them.
Also if ribbons are not made for the Government, they do not need the Letter-Number combo.
There was a time when NS Meyers came out with their Fetha-Wate type bars, see date below, probably cheaper to make and so of course Wolf-Brown had to jump in to compete and made their version, they did not last long though, probably as they were flimsy and would come loose easily and so they went back to normal "Brass" mounts.
These are ones I have and there are probably more examples.
