This pocket calculator was manufactured in Bulgaria by Isot. Bulgaria had one of the largest electronics industries in Eastern Europe before the fall of the Iron Curtain. When Japanese and American-manufactured pocket calculators became widespread in the West in the 1970s, the Eastern Bloc countries lacked the technology in terms of integrated circuits and displays to compete. Calculators such as this used imported technology produced by firms such as Rockwell and Texas Instruments. As well as being used behind the Iron Curtain, Isot's Elka machines were actually available to buy in Western Europe.
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