Solving the mystery of red quarters: why are some coins painted red?

Have you ever received a quarter in change and noticed it had a peculiar red tint or paint on it? These "red quarters" have been circulating for decades, often leaving people scratching their heads about their origins and purpose.

The most common explanations for red quarters are that they were used for testing coin-operated machines, as "house money" for free plays in businesses, or for free laundry in apartment buildings. In the past, repairmen would use these marked coins to avoid being accused of stealing when checking pay phones, vending machines, or laundromat washers. Some businesses would give red quarters to preferred customers for complimentary games on pool tables, pinball machines, and jukeboxes.

According to this video, in the days of jukeboxes that charged a quarter for three plays, restaurant owners would often prime the machines with their own red quarters to keep the music going, later collecting them back when the jukebox owner emptied the coin box.

Previously: This 1960s coin sorter is an electromechanical delight