Developed in 1972, the HP-35 was Hewlett Packard's first pocket calculator and the first pocket calculator ever to have transcendental functions. Twenty HP engineers spent two years and approximately $1 million developing it. Even though the calculator cost $395 for consumers, HP sold exponentially more than the anticipated 50,000 units.

Calculator (A):
Casing is a tough, black plastic; calculator buttons are of various rectangular sizes and colors of black, blue, and white; most of the buttons have the function or number printed on the buttons themselves; in addition to numbers 0-9, other buttons include, e.g., sin, cos, tan, 1/x, etc.; On/Off switch is in top left-hand corner; LED display screen has a reddish tint and spans the top of the device; back of device has a 3-prong input (possibly for power source), a removable panel; and a list of button and function instructions.

Calculator Case (B):
Case is black leather; pocket opening is at the top and attaches to case via velcro; no writing/symbols aside from a small HP logo on pocket opening.