At first glance I thought that also but the 57 Plymouth was a full size cap. I still think it’s Mopar or Ford, not aftermarket.
Mopar did have a small cap like it 57-59 and the Dodge Town wagon/panel had them also up into the 60's - some were painted a silver/gray color.
I believe the same cap was also used on half ton Dodge trucks from 1960 to about 1966. Some of them are stainless and some of them are silver painted steel, not sure if the painted ones ever ended up on passenger cars or if those were pickup truck only.
Namsco and others sold hubcaps like these and called them Fury caps... Here called Warrior...look at "M"
Getting sidetracked now but I have one of those "Moon Duster" caps shown in the ad above, those fins were die cast and the cap weighs a ton. The ends of the fins are not really finished and don't look like they were designed for that purpose, I thought maybe it was home made. I wonder if they got a bunch of chromed fins from something else and just attached them to hubcaps? It's very strange looking in person.