I'm assuming it was designed to teach you basic concepts like conversion and output, but still remain reasonably cheap.
It would have been better to use one of Intersil's chips, but that wouldn't teach you much.
Was just watching a video on the IM-1212. Turns out it has a 0.00 to 1.99 2-and-a-half digit range. It uses another single element tube/lamp for the "1" digit and an "overload" neon lamp when out of range warning. Later models were changed to use 7-segment LED displays (IM-1210 model). Apparently it was also branded under the DeVry brand (the now defunct electronics school I assume) and the Bell & Howell version you have. Interesting bit of kit and a good intro to learning how test equipment worked back then.
I've seen Heath, B&H and Schlumberger, but never a DeVry unit. B&H did the school thing for a while as well.
I'm going to press it into service as a pilot light with numbers for the 5V rail on my network rack.
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