Nice! Why have I never seen an aluminium slide rule? Also, for the benefit of us non-Americans, what approximate age is "high school"? At school slide rules were the only permitted calculating machines in maths classes up to age 16 in my day (academic year 1982-83) (requirement was dropped a couple of years later). I went through a series of cheap plastic ones and ended up with an expensive plastic one - I asked the local stationers for a replacement cursor and they sold me this really nice slide rule for the same price (one pound) just to get rid of it! This too has lost its cursor, tho' I believe I still have the rule somewhere. More recently I bought a decent wooden one for a similar price at a car 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. Wow! On a 7 foot rule you should be able to get four sig. figs without too much interpolation anywhere along the length. Or are the markings too coarse for that? Philip.