I finally managed to make a screenshot of my Psion MC400 laptop. I have spend several hours working on the machine and it is surprisingly user-friendly and well-designed (please remember that it’s a 1989 laptop).
Yes, the software is functionally limited but it is user friendly AND effective (note that there is only 256 kB or RAM available for both main memory and the ramdisk so the software have to be small and simple). The keyboard shortcuts are sometimes unusual but easy to remember so it is easy to start to work with the machine.
I noticed just one problem – I cannot find image viewer so I can take screenshot (Shift+Control+Psion+S) but I can only use it as a wallpaper… :-\
Fortunately it is easy to move the file to a workstation and to use pictopnm, for example (get it here).