(Space) S/N 40 Satellite
Not even a decade after Sputnik, man's first successful earth orbiter, which was just a simple radio beacon with four antennae, and this schematic is evidence of advances that had been made.
But this wasn't just a satellite, this was part of the "Transit" program, an early proto-GPS system aimed at navigation during the cold war era escalation. It's been described that "The development of Transit, more formally known as the Navy Navigation Satellite System, was arguably the largest step in navigation since the development of the shipboard chronometer". While Transit used only Doppler shift measurements to determine position it fulfilled the need for real time data with good resolution.
Condition is very good. Size is approximately 16 x 20 (inches)