My first scanner in the 1970s was a SBE Opti-scan, which used plastic cards that had small removable adhesive squares covering clear holes in the plastic, so it worked similar to the punch card type. The manual had a lookup table that indicated what "holes" to uncover for a specific frequency.
Opti-Scan SBE-12SM
Since then many scanners, and right now my collection includes a couple of near mint Realistic's, and a JIL SX-400 with an up-converter.
Opti-Scan SBE-12SM
Since then many scanners, and right now my collection includes a couple of near mint Realistic's, and a JIL SX-400 with an up-converter.