Explore the fascinating journey of reverse engineering and recreating the HP-35, the first handheld scientific calculator, in this 35-minute conference talk from Hackaday's Remoticon 2021. Delve into the world of 1970s electrical engineering as Rob Weinstein meticulously dissects the original patent, deconstructs the device to its transistor-level components, and ingeniously rebuilds it within an FPGA. Gain insights into the HP-35's historical significance, its intricate inner workings, and the innovative "barber pole timing" mechanism. Discover the complexities of the serial adder-subtractor and examine detailed design documentation, including front, lower, and back side layouts. Learn about the operating manual and get a comprehensive understanding of this groundbreaking device that revolutionized scientific calculations half a century ago.