Why the stamp was issued: This 5¢ stamp is what the USPS calls “change maker” postage. These stamps with denominations of 1¢ through 6¢ are produced to make up the wide variety of rates for third-class parcel post, which has many combinations of charges for weight and distance. These stamps were also useful when first-class rates went up, before the USPS could release stamps at the new rate.
This was also the second US stamp to honor Muñoz. A 1949 stamp (US #983) commemorated his election as Puerto Rico’s first governor.