No Batteries Required

This is my 6" Slide Rule (it was my Dad's).  An essential tool for many before the birth of the electronic computer.  You can do some rather wonderful calculations with it - and do them quickly and accurately.  I've largely forgotten how to use it (and I've lost the cursor) but I tried a few today.  The old grey matter did get there eventually -  but a computer is much quicker.
Nice to see it again - shame about the cursor.