It is well-known that factories during the Porfiriato used scrip, at least in part, to pay their workers or give them advances, though specific instances (and example of such scrip) are rare.
Numerous accounts tell that company stores deducted a certain percentage of the value of these vales. According to Dawn KeremitsisDawn Keremitsis, La Industria Textil Mercantil en el Siglo XIX, Secretaría de Educación Pública, 1973, pp. 202-3, this discount was between 10 percent and 12 percent of their nominal value. According to an article in La Voz de México La Voz de México, 11 January 1907 the discount was 25 percent. At the Magdalena and Santa Teresa mills located in the surroundings of Mexico City this rate seems to have been 18 percent per weekFriedrich Katz, La Servidumbre Agraria en México en la Epoca Porfiriana, 2004, p. 114.
It is not clear whether these accounts refer to the discount made when exchanging scrip for money, or when purchasing at the store with scrip, although the former seems more plausible. We should understand this discount as the interest rate the company store charged for the credit it gave, minus the five percent it paid in commission.