stamper: a workman whose job is to form or cut out by applying a mold or die (either by hand or by operating a stamping machine)
person: a human being
plutonium: a solid silvery grey radioactive transuranic element whose atoms can be split when bombarded with neutrons; found in minute quantities in uranium ores but is usually synthesized in nuclear reactors; 13 isotopes are known with the most important being plutonium 239