My searches on the basic 1 have come unconclusive. I suspect that like the alleged pencil 1 they don't exist commercially (maybe they are protos that got refurbished...)
do you have the possibility of dumping the cassett thank you for the cassettes?
thank you for the cart info. Very useful. I'll pass it around.

regarding the hmg 7900 it's actually a console (see the link) of the soundic family.around 10 carts exist.