Certainly a ball peen hammer that could be encouraged to go rusty for scientific purposes. I wonder if it would work well enough striking a sheet of aluminum foil on a hard flat surface?

It wouldn't be weird for someone in the south of France to have a rusty pétanque ball.

Hammer faces would work (def wear goggles!!!). Hit the face of the disposable one with a mixture of hydrogen peroxide, vinegar and salt and wait an hour.

Joining the thread to see where iron balls can be sourced.

Some vendor on AliExpress? Those Lucky Iron Fish?