[Animats]

The concept of measuring how much ink appears as the text passes a vertical slot came back again in the 1950s. MICR codes, the numbers that appear on checks, are read that way. [1] Or at least were in the original implementation. The ink was magnetized and the paper went past a one-track magnetic tape head. The waveform for each symbol is unique. The recognizer is more like a bar code reader than an OCR system.

There are only 14 characters in that font - the digits 0-9 and four special field identification symbols. The 1970s "futuristic" text fonts which look like MICR symbols are purely decorative.

[1] https://en.wikipedia.org/wiki/Magnetic_ink_character_recogni...

[flopsamjetsam]

Fascinating, I never realised that's how they work. I found a list of characters and their waveforms. [1]

[1] https://smartcheque.com.au/general-info/about-micr/micr-char...