Still have my old slide rule AND the hanimex calculator (1975 vintage) that replaced it. Well sort of replaced it .. we werent allowed to use calculators at school HAHAHAHAHA !!!!
http://www.vintagecalculators.com/HanimexBC900_1.jpg
IT was amazing how accurate a slide rule could be IF you knew how to use it .. 2 decimal places was a breeze and even with a bit of parrallex error