Nintendo's line of Game & Watch LCD handhelds gave the company a foothold in the world of portable gaming which would prove to be invaluable by the time it launched the Game Boy in 1989.
While the Japanese firm quickly switched focus to its dedicated monochrome handheld from that point onwards, the Game & Watch market was (briefly) still an ongoing concern – as is evidenced by what appears to be a prototype version of Game & Watch Tetris.
It's difficult to tell at this stage if the unit is 100% authentic – it appears to use the Game & Watch Safe Buster shell – but if it is the real deal, then it shows a willingness to experiment with the core concept of Tetris, which – back in the late '80s – was still being established.
In this version, blocks drop in from the top screen, and instead of moving the block itself, the player instead controls the playfield on the bottom display, shifting it left and right to accommodate the falling shapes.
Nintendo's Game & Watch line was created in 1980 by the legendary designer Gunpei Yokoi, who would also dream up the Game Boy. As well as offering innovations such as dual screens and clamshell cases, the Game & Watch line would mark the first appearance of the "cross" D-pad design, used in 1982 for the Game & Watch version of Donkey Kong.