I've just bought one of the re-makes of the HP 15C calculator. It's not a true replica replica of the thirty year old original; inside it's an ARM processor emulating the original processor in turn running the original firmware. It wasn't hard for HP to make because the closely related HP-12C financial calculator has been available continuously since the range debuted in 1981, and the hardware has been kept current. The 12C is a cult classic amongst Wall St types, but was also for a long time the only calculator certified for use in US financial professional exams, so the textbooks are built around it, RPN and all. The 10/12/15/16 originally differed only in firmware and keycaps, so although only the 12C had been ported onto later hardware versions, there was no reason why the other versions would not work. Indeed, a re-issue HP-15C flashed with the HP-12C firmware has been spotted in the wild. I guess it's only the niche-ness of the market which means that they haven't re-released the HP-16C programmers' calculator.
But what it hammers home is how products decay over time. I've now got probably the three major "modern" mid-range HP scientific calculators: the HP15C (1981--1989), the HP32Sii (1991--2002) and the HP35s (2007--). The 32s added symbolic entry of functions which you can then integrate and solve (the 15C requires that you write a program which returns the value, rather than being able to enter it symbolically) and the 35 is really only a 32sii on steroids. The 15C however has a matrix mode which is rather nice. But my 35s, which I've had four or five years, is on its second set of batteries, while the 32sii, which I've had for about twenty years, is also only on its second set. As you can see in the photograph, each iteration is physically larger than the one before. The 15 has more keys (aside from the silly "cursor" style things on the 35). The 15 is thinner, lighter and barely less capable. What's got better in thirty years?
ian
