The ET calculator series began when Braun obtained Omron's calculator design, starting off with the ET 11 Control model in 1975. Over the next decade the design would continue to change, showing the interactive nature of design, and how it’s subtle yet thorough changes are what makes it such a strong design. In the ET 55, details such as the rounded bottom corners, the simple color scheme, the buttons polished finish and the covers logo placement are all design decisions done through thorough research and with intentionality. This refinement is likely why the ET 55 remained in production longer than any of the previous models.
