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At least three different types of keyboard have been discovered.
PET-derived Mitsumi hybrid
This appears to be the original keyboard, using the guide shaft plate, sliders and keystem adapters from a PET keyboard (like that of the Commodore 8032-SK), but a revised keyboard matrix. The shift lock switch is likely to be Futaba lock the same as in the later keyboards. Black tape covers up the unused holes for switch positions not used.
Discrete rubber domes
Found in a 1983 Revision D VIC-20, from below this has the same general design as the later keyboard (and that of the Commodore 64), but instead of using "hybrid" switches, it has sliders over discrete rubber domes that appear to be glued to the PCB. The shift lock switch is still Futaba lock.
This has an identical arrangement to the Commodore 64, with cruciform mount conductive foot Mitsumi hybrid switches, and a non-keyboard switch for shift lock.