If you want to add a quick set of stamps to your passport, take a day trip to Anguilla from the French Side. You'll get a French exit stamp, Anguilla Entry Stamp, and a French Entry stamp when you return.
It's $40 round trip for the ferry, and a rental car on the island cost me $30 cash for the day.
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Aaah, but is country visiting equal to passport stamp collecting? Like Train Spotting?