US Stamps - Progress in Electronics - full sheets

Description

In 1973, the US Postal Service issued these four stamps to commemorate Progress in Electronics: Full sheets of 50 stamps. - 6 cents - Marconi spark coil (Scott # 1500) - 8 cents - Transistors (Scott # 1501) - 11 cents - DeForest Audions (Scott # C86) - 15 cents - Microphone, Speaker, Radio tube (Scott # 1502) Selling the four sheets as a lot.