National Union GI-21

The GI-21 is the larger counterpart to the GI-10 , both manufactured by National Union as part of their &ldquo;Inditron&rdquo; line of display tubes. This places it among the earliest Nixie-style tubes ever produced, even predating the term &ldquo;Nixie&rdquo; itself that was coined by Haydu Brothers (later Burroughs) in the late 1950s. Like the GI-10, the GI-21 does not feature a dedicated anode…