Sinclair Scientific
Let's not forget the Wonderful Sinclair Scientific calculator...
I was a 24 year old electronics engineer in 1974 working in the aerospace business. Electronic calculators had only been around for a few years and were VERY expensive. The Hewlett Packard HP35 had appeared a year or two earlier but was, I think, about £150. A lot of money in 1974! Then along came Sir Clive's Sinclair Scientific at under 50 quid. In true Sinclair fashion, it was a bit slow and clunky but it could do nearly everything the HP35 did.