The NES Four Score is an accessory for the Nintendo Entertainment System created by Nintendo. It allows four-player gameplay on certain games that supported it. The Four Score was released in 1990.
On the Four Score itself, there is an option to switch between two-player and four-player modes and turbo
A and B buttons that would give any of the connected controllers a
turbo boost. The Four Score can also be used as a controller extension
cable because the wire which leads from the accessory to the NES has a
length of a few feet.
A similar product is the NES Satellite (which, unlike the NES Four Score, is wireless), which allowed for an even longer distance between the controllers and the NES.