Multiplication on a 120-year-old calculator - GIF

[BuffaloJohn]

Actually, this is multiple additions rather than multiplication. The user set the initial value at 4.27 and each rotation added 4.27 to the result (0 -> 4.27 -> 8.54 -> 12.81 -> 17.08 etc.)

If for example you wanted to multiply by a second large number, you have to count rotations on that number. 4.27 * 367 would be a challenge.

And then, you also have to keep track of the decimal point. If you wanted to do 4.27 * 3.67, you would have to do 4.27 * 3.67 and then divide by 100.

I think it would be easier to do the math with paper and pencil...