From at least the early 1940's until the savings stamp program was ended on June 30, 1970, the savings stamp program focused first on funding U.S. participation in World War II and later primarily upon encouraging thrift among the nation's youth by persuading them to save small sums. Stamps were sold in denominations (face values or amounts) of $0.10, $0.25, $0.50, $1.00, and $5.00. Stamps were acquired from post offices and sold in schools to students. Albums and patriotic materials were made available to schools to promote the program. When as little as $18.75 had been saved, a $25 (face amount) Series E savings bond could be purchased. Stamps were non-interest bearing and unregistered.