ISO-IEC-9995-4 first put out in 1994 talks about the 10-key layout for keyboards. none of this directly answers calculators, but it might be related. https://e

ISO-IEC-9995-4 first put out in 1994 talks about the 10-key layout for keyboards. none of this directly answers calculators, but it might be related. https://en.wikipedia.org/wiki/ISO/IEC_9995 https://en.wikipedia.org/wiki/ISO/IEC_9995 surprisingly, the 0 is centered under the 2. it can optionally be extended to under the 1. other surprise is that the backward telephone layout is an option - if i ever got a keyboard like that, i'd be annoyed.