How to open a 49G?

[Thomas Okken]

(11-18-2018 12:30 PM)Maximilian Hohmann Wrote:  I also very much like the HP-67 as an overall package. All the functions I ever need are there, the keyboard is about the best of any calculator ever made and it has a red glowing display. But it would not be my winner because I don't like the brownish colour scheme much. Why couldn't they stick with the black scheme of the HP-65?

I'll venture a guess: the shift key scheme used on the 65, with f, f^-1, and g keys, wasn't flexible enough for the 67, so they needed three different shift keys, and therefore three different colors. The yellow and blue legends could be printed on the faceplate, but what color to use for the legends on the keys? You need something that contrasts with both the white number keys and all the other non-white keys. Black was an obvious choice because using any other color would have made the calculator look too gaudy / visually busy, but to use black, you need even the dark keys to be somewhat light, in order to get sufficient contrast.

I don't think this was a design choice they made lightly (OK, I don't think HP ever made calculator design choices lightly!), and they must have been pleased with the result, because three years later, they did the same thing with the 34C: gray keys where all the other Spice models had black ones.