Bet you haven't seen one of these before!!! :)
The SG Commander was a updated joypad released by Sega as an upgrade to the standard one. It includes rapidfire and autofire selectors for buttons 1 and 2, located above the buttons. The front of the joypad is also more ergonomical and aesthetically pleasing. It is clear that the SG Commander is heavily influenced by the NES joypad; The D-Pad and button designs are very similar. Perhaps this is why it was never released in the US. This is quite a rare accessory as it was discontinued around 1991 in the UK.