What term describes the study or collecting of coins?

The July 1944 plot code-named Operation Valkyrie was an attempt to kill which leader? What name is given to the code of behavior expected of a medieval knight? "Coffey's Hands" was the third installment of which Stephen King novel, published in serial form in 1996? Coffinite, a mineral first described from the Colorado Plateau in the 1950s, is an important ore of which radioactive m… Jerome Robbins's ballet "Fanfare" debuted in New York in 1953 on the same day which monarch was crowned? The first Olympic Games held in the United States, in 1904, coincided with a world's fair in which city? What name, reportedly coined by a mathematician's 9-year-old nephew, refers to 1 followed by 100 zeros? Which phrase, coined by Boston's Columbian Centinel in July 1817, often describes James Monroe's presidency?