They may be drive screws…. Common for them to be used for the plates. Most times there is a thru hole so one can pop the drive screw out from the inside. I have seen them without the thru hole as well, but that seemed less common.
If you can get a good pair of vise grips on the head you “might” be able to turn the drive screw out…..if memory serves it should unscrew counter clockwise. Just some break-time thoughts.
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