Yes they're plastic but they were exclusive to the Eagle and said 4x4 in the middle.
You get a star for knowing about “dog dish” hubcaps and extra points for noticing how well they go with red wheels. (Your name indicates that you are probably old enough to remember these, instead of just having heard about them from your grandfather.) :)
The steel hubcaps on W123 and earlier Mercedes are very nice indeed, but I do have a thing for the minimalist plastic ones on W201 and W124:
Since Doubblewhopper2.0 posted such a shitty picture (sorry), Corvette Rally Wheels are the king of hubcaps imo.
These are the best