The Otis King Calculator!

This goes back to the early sixties, when I was an apprentice CA, and always looking for easier ways of doing things. And I found (in Exchange & Mart, I think) this circular sliderule!

Would you believe, that by simply setting the upper and lower scales (the white bits covered with numbers), shoogling the central cursor (the black bit in the middle) around and resetting the scales, you could work out what £250 would become in 14 years time at 5% compound interest.

The answer is £528 10s 0d.

All very fine until decimalisation and a recession come round, when the answer becomes tuppence ha'penny!