Request. HP calculators (desktop/handheld) production timeline

[Greg]

It's interesting to see the HP-55 and HP-25 on the same year in your chart. I'm not doubting your sources and I think it's probably a matter of a lot happening in the same year.

The HP-55 is a classic series calculator which uses the same processor as the HP-35, though there may have been some tweaks over time.

The HP-25 is one of the first of the woodstock series with the new processor. There are different opcodes (and many of the old ones) and they merged the two parts of the processor into a single chip.

My interest has been in seeing where the HP-25 came from and it seems to have come from the HP-55. New processor, new form factor; but internally still 49 steps, also stored in RAM rather than the HP-65's rotating 600 bit register, (internally) the user program counters are both stored as actual step numbers (instead of "62F" and similar on the HP-67/29C).

Hope this adds a little to your understanding of the timeline. It'd be interesting to spread out the year a bit (might not be practical) and maybe know more about the development timeline (might not be known or, if it is, might not have hard date like "today we're starting on the HP-nn").