This item is aparallel port joyport expansion adapter that allowed someone to play a '4 joystick game' such as Hired Guns etc.
This adapter allowed joystick 3 and 4 options to be enabled in many games of the day by plugging into the parallel port of the amiga.
It was designed by Proton Palace (J.D. Robbins was the circuit designer) circa 1993 and sold well.