Progress in Electronics Block of Stamps

GUGLIELMO MARCONI Art Craft 1874-1937 INVENTOR OF WIRELESS TELEGRAPHY OFFICIAL FIRST DAY OF ISSUE MARCONI SPARK COIL MARCONI SPARK GAP sin Electronics SERIES OF 1973 MEN Marconi Spark Coil Marconi Spark Gap NY 6c Progress in Electronics JUL 10 1973 Marconi Marconi Spark Coll Spark Gap Judem Findsey Judson 4314 Nelson the Peoria, Ill. 6c Progress in Electronics FIRST DAY OF ISSUE