A reproduction of the Datamath II calculator made by Texas Instruments from 1975
(Calculator)[https://dkallen78.github.io/datamath/calculator.html]
(Manual)[http://www.datamath.net/Manuals/TI-2500-II_US.pdf]
You can use the number pad or the regular keys to input to the calculator. C is c, CE is v, and % is p.
Since I don't have a physical Datamath II to play with, I based all of my functionality on what I saw in the manual.
Some of the interesting things I wasn't expecting were the functions for finding the square and reciprocal of a number. I also didn't expect the constants and repeating addition/subtraction (which is often achieved by repeated use of the "=" key).