What’s really nice about the Curta is that by thinking about the maths problem you want to solve in a logical manner you can minimise the number of handle rotations to calculate the answer. So for example, finding the answer to 9×9, 99×99, 999×999, 9999×9999, 99999×99999, 999999×999999, or 9999999×9999999 all only take two handle rotations to get to the answer. But it gets even better than that. The Curta’s reign as calculator supremo of course came to an end with the advent of the electronic pocket calculator, but now look again at that last calculation in the set above. The answer the Curta (Type II) gave me to 9999999×9999999 was 99999980000001 which as you note is a 14-digit number. Now go and check on my (not inexpensive all-singing and dancing) electronic calculator and what happens? Can’t supply me with all the significant digits can it! Gives me 9.999998E+13 as an answer – not as accurate as the Curta! WOW! Actually have to go to the computer and run Mathematica to get the full run of significant digits – so there you go. O.K. so my electronic calculator can give me square roots, trig functions, and all the other fancy stuff at the press of a button – but my pocket difference engine can supply me with more significant digits in two handle rotations. Just how cool is that?