The Gemini/Cosmo have had exactly the same layout as the Psion 5 from prototypes to final product, right down to the odd irregular spacing around the edges (I'm pretty sure the prototypes did use a Psion keyboard). I was wondering if this was to allow the old moulding tools to be reused.
No. As I recall them, the Psion Series 5 keys were a tad deeper (and had a tad more travel), which worked, since the entire device was 23mm thick. Also, I read that, for the Gemini, they had to redo the tooling for the keyboard "several times" before they got it right, which was one reason the Gemini got delayed. Even then, the Gemini keyboard had certain issues the Psion keyboard didn't and vice versa, so no, while the Gemini keyboard is made to look very much like a Psion keyboard, it is a unique design.
The Gemini mock-ups indeed used a Psion keyboard. On early marketing photos, one can see that there is text on the front of the space bar. They've scaled the image to make it kind of unreadable, but it says "Backlight". That's for the electroluminescent screen backlight of a Psion. They used to have the image in better quality and I have saved a copy of that, but since I don't own the image, I cannot legally make it available online. I did find this, though:
[Edit 2021-May-03] When trying to fix a broken image link, I noticed that this version of the forum software would insert the 20MP image at 100% scale, so here is a very small crop (less than 1%) that I'm going to claim is "fair use" to illustrate a particular point in history
This is a link to (a heavily compressed version of) the whole image
http://static.androidiani.com/wp-content/uploads/2017/04/Image4-1.jpgAccording to the EXIF of the version I have, the photographer is Pietro Cardoso.
Note that the Caps Lock LED is rectangular, not round and that the "Planet/Alt" key just has a line of text (it says "Menu") on it. Further, one can download the official Gemini User Guide, from
http://support.planetcom.co.uk/download/Ge...DAUserGuide.pdfand have a look at page 19, where the Caps Lock LED (labelled "Power LED", which is also true) also has a rectangular shape. Probably the sketch was drawn early on, before the keyboard design was finalized, so maybe they thought of using a rectangular Caps Lock LED at some point. [/Edit]
The "odd irregular spacing around the edges" is probably because the Psion and Gemini keyboards approximately respects the "correct" sideways offset between the letter rows. Q is supposed to be 1/4 of a key to the left of A, while Z is supposed to be 1/2 key to the right. Many other PDA-type devices do as they please with these offsets, and some even skips them completely, putting their keys in straight columns. Even the Psion and Gemini cheats a bit, as on a "real" keyboard, 1 is supposed to be 1/2 key to left of Q, which equals 3/4 of a key to left of A, which in turn means that each alphanumeric key gets a unique horizontal position, to make room for the mechanical levers by which typewriter keys, once upon a time, were attached to the rest of the mechanism.