Featuring Charles Steinmetz, for his electrical theories; Edwin Armstrong, for his frequency modulation research; Nikola Tesla, for the induction motor; and Philo T. Farnsworth, for creating the first television camera.

This block is in mint condition and has never been hinged. The 20 cent stamps were issued in 1983 in the United States and showcase historical figures who have made significant contributions to the field of invention. 

The orange color adds a pop of vibrancy to any collection. This block is ungraded and uncertified, but it is a great addition to any collection. 

The face value of the block is 0.80.