Pennies are first introduced in Chapter 2 when J.W. bets Ivon he can guess her profession and then hands her a roll of pennies when he loses. Later, when she, Ximena, and Father Francis go to the morgue to view Cecilia’s body, Ivon notices a plastic cup full of “blackened, corroded coins mixed with pennies” (52). Irene, in captivity, sees a chalkboard with three columns—one for pennies, one for nickels, and one for dimes—and frequently hears her captors reference pennies. Ariel tells Junior that a busload has arrived with “[s]ix pennies and the other half of your nickel” (221), and Junior calls a girl he’s filming “another lucky penny” (268). The suggestion that the coins represent victims is confirmed when Ivon is in the Border Patrol car with J.W., who refers to Irene as “that nickel” (283) on a phone call with Junior. Because he also called Irene “a cute little lucky penny” (284), Ivon realizes that they are headed to the ASARCO copper plant and that J.W. runs a business that live-streams the rape and murder of young girls and women. 

The meaning behind the coins is revealed in Chapter 34, when pennies are found inside and around the mutilated body of Mireya Beltrán.