Ah, it doesn't seem to be the same machine then...
The Videopac used cartridges and had a rather useless keyboard (maybe to look more like a computer
) . In fact, it is a clone of the Magnavox Odyssey. Your nephew's machine might very well be a Videopac of first generation. Mine was a Philips Videopac + (Odyssey 3 clone), the last generation.
Could you Pong be this one here