I still have the HP-45 calculator that I bought as a junior at the U of M. The HP-45 was the second hand-held calculator produced by HP, following the HP-35 which debuted in 1972, my freshman year. Calculators were so outrageously expensive at the time -- the HP-35 initially cost $395; the HP-45, $800 -- that they were considered an unfair test-taking advantage over the bulk of students who could afford only slide rules, and thus were banned during tests until my senior year. They had a demonstration model available for anyone to play with at a counter in the engineering bookstore, and I would sometimes go there late in the afternoons to use it on my physics homework. Man, how I lusted to possess that marvelous device, which could so effortlessly calculate standard deviations, convert between radial and rectilinear coordinates, and conjure values of transcendental functions with to impossible precision faster than an undergraduate could say "mantissa". Kids today -- what with their umpty-GHz laptops and fancy spreadsheets -- will never understand how easy they've got it! :-) Prices for advanced electronics, then as now, dropped rapidly. I could afford the HP-45 midway through my junior year only because it had within a year and a half dropped from $800 to $400. (Bear in mind that a typical textbook would set you back about $25 in those days.) My old HP-45 is not for sale -- it holds great sentimental value for me -- but I would be willing to loan it to you for a few days, if you'd like to show it off to your math students. -- Dean BTW, Wikipedia has a fascinating article on the HP-35 et sequelae, where you will learn that, "The HP-35 was exactly 5.8 inches long and 3.2 inches wide. This was the size of William Hewlett's pocket, hence 'pocket calculator'." http://en.wikipedia.org/wiki/HP-35 At 04:14 PM 7/19/06, Dan Drake wrote: >I'm teaching a math course for elementary school teachers, and today we >told them about Reverse Polish Notation, just to make them think about >order of arithmetic operations. > >It would be nice to actually own an RPN calculator, so one could show >students that this isn't just an abstract curiosity. Does anyone have an >old RPN calculator that they would sell me, or know where I could get >one? > >Dan