It is a 6-plus-6-keyboard with six rows. So there is the same fingering in all scales and the thumb has its own rows for a better moving on the keyboard.
For an 88 note (full size) keyboard, there would be 264 keys in total, with each note playable by 3 keys in vertical alignment. In the picture, the white keys have been coloured to show how the keys are interconnected.
Now the Jankó keyboard is used for an electronic keyboard, the Chromatone 312.