Last week, I shared here about the HP-14B 50th Anniversary Edition that a friend kindly lent me. It as really cool. As a former HP employee, I presume that she witnessed a few historical moments of the electronic industry. I would love to interview you Joanne :-). She was kind enough to allow me to harbor two of her beloved calculators. One of them is a gorgeous HP-21 that I cannot resist presenting you tonight. And what could be better to unwind after a busy work week? The HP-21, code-named Pumpkin, was introduced in 1975 (produced until 1978 – this specific model was built in the 2nd week of 1976 in America and has a serial number of 7058). The HP-21 is the scientific model of the Woodstock series. As often, Hewlett-Packard derived the base model to target specific segments: business with the HP-22 and engineering with the programmable HP-25. The HP-21 is the direct replacement of the HP-35, the world’s first scientific pocket calculator. Although smaller and supposedly cheaper to make, the 21 packs more features for fewer bucks. Its ROM holds ~30% more microcode, which allows for functions such as trig in radian, polar/rectangular conversions or 10^x. Comparatively, the 21 has only 30 keys, where the 35 has … 35 of them! (which is, by the way, the origin of the model’s name). Unfortunately, I could not open the battery door without forcing too much so I could not power it up yet. Because the batteries likely leaked after 40 years, I will take my time with this beauty. As soon as the pack is rebuilt, I will make a direct comparison with my 35 and 25C for you.