SET 4 FIRST DAY ISSUE COVER 6 CENT SPACE RACE PROGRESS ELECTRONICS FDC USPS 1973

This is a set of 4 first day of issue stamps from the 1973 series, "Progress in Electronics: Spark-to-Space Salute." Kept by a collector who stored them safely in plastic sleeves, these first covers are in excellent condition. The stamps feature: Marconi/telegraph, micro electronics/transistors, Apollo 11/communications, and DeForest/radio. I am not a stamp collector, so if there is important information that a collector would need, but is not included here, please let me know, and I will be happy to give you that information.