<Nice! Why have I never seen an aluminium slide rule? No idea, here in the lat 60s and early 70s they were one step better than plastic but not as expensive as the bamboo or mahogany ones. <Also, for the benefit of us non-Americans, what approximate age is "high <school"? approx 15-18 years. <At school slide rules were the only permitted calculating machines in <maths classes up to age 16 in my day (academic year 1982-83) In the late 60s and early 70s slide rules were permitted where the calculated value was part of the answer for geometry, trig and calculus 90% of a given problem was the work and 10% the actual numeric result. In the technical (EE world) it'was expected you knew how to run a slipstick and answers were expected to be accurate to three places plus correct exponent. I was the first one to bring an electronic (pocket almost) calc but I still kept a 7" stick for quick trig functions. <boot sale - still in box with plate glass cursor. I also have a special <purpose cardboard one with two slides that is meant to calculate the <flow of water through pipes of various sizes, materials and gradients. I still have a few special ones including a plasticized paperboard one for coil spring design. The 15" I have is good to 5 places on the left and 4 on the right for basic finctions, trig and logs were good to 4 and 3 places. Allison