Maybe the OP didn't mean counterstamp. There are foreign coins struck over an existing 8 reales. That may be what he was thinking.
I was thinking if the US Mint ever counter-stamped foreign coins. Particularly for the 8 Reales, the Brits counter-stamped them, so I was looking for a US example, given its prominence in the colonies. But it looks like the US simply adopted the 8 Reales altogether.