These plates are proliferating like flies. This particular plate is a fake US plate with a solid base bullet embedded in the lower half of the S. The hole in the plate does not match the size of the bullet.
These plates come in both US as well as CS plates, and are NOT limited to the common oval. Have seen several specimens in rectangular plates as well as state plates!!
Before purchasing any bullet struck plate, check with an expert and demand the right of inspection and return if found to be not authentic.