The Kes-Add (or Kesling Pocket Adder) was a simple 4-digit counter/adder which was patented in 1948. It can be used for adding and subtracting 4-digit numbers. It would come with a stylus that could be used to dial in your starting number and then add another number. A simulation is below. (This simulation is for students in MSE 105; you will work out details on how to use this to add and subtract.)