HP-35
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The HP-35 was Hewlett-Packard's first pocket calculator and the world's first scientific pocket calculator: a calculator with trigonometric and exponential functions. It was introduced in 1972. Wikipedia
Introduced: 1972
Dimensions: Length: 5.8 inches (150 mm), width: 3.2 inches (81 mm), height: 0.7–1.3 inches (18–33 mm)
Discontinued: 1975
Display size: 15 digits (decimal point uses one digit), (±10±99)
Entry mode: RPN
Memory register: Four-register operational stack with one memory register
Power supply: Internal rechargeable battery or 115/230 V AC, 5 W