Systel K3 1040-1000-00 keyboard
The images below depict a Systel K3 keyboard, part number 1040-1000-00; they are archived from eBay listing 113486301918 “Rare Vintage Keyboard Systel K3”, since deleted. This listing belonged to eBay user jkulp5200.
This is a General Instrument S700 Series foam pad capacitive keyboard, confirmed by the manufacturer and series information printed on the bottom of the PCB. This keyboard has white-on-black double-shot keycaps.
Curiously, the removable cable connects into a downward-facing modular jack (possibly 6P) on the bottom of the cable. The existence of stick-on rubber feet leaves an interesting question of how this keyboard was used, such that it could sit on a flat surface with the cable projecting vertically downwards; possibly it used a special right-angled plug.