Two of the Dempa Micomsoft releases used a special controller with two D-pads. These games required two sticks in the arcade, and would be nigh unplayable on a console without two pads.
The controller has two D-pads and two buttons. Micomsoft went to some effort to make the internal design of the pad very easy to duplicate, and it should work fine as a regular D-pad for any game that doesn't activate the second pad.
The mechanism is simple: A 74157 (the same as in a 6-button pad, Genesis or PC Engine controller) is used to select which d-pad is active.