From: Frank McConnell <fmc(a)reanimators.org> These were common in the 60s. Driving nixies has one problem you need a transistor that can handle at least 60-80V, early transistors werent cheap (those that could). Also you needed high voltage (170-220Vdc) for nixies, plus resistors for current limiting all adding up to to a lot of space power and heat. Transistors that could switch 100ma@6V were common and cheap so the same diplay idea was used. There were other reasons with respect to readability and diplay color as well. Another config that was used is a 7segment where each segment was a wedge of plastic forming the bar and a lamp (or later led) behind it. These preceded the LED based 7 segment at low cost. For those that don't know there were also filliment based 7segment displays (have a bunch) for the early growing display market. They were aimed at the problem of good leds at that time being expensive and not terribly bright. My first freq counter has four of these and still works 27 years later. You are closer to right. Allison