A/T Button on the 2003 Z's in Japan.
 

I have a Japanese auto magazine. Can't read it because it's not printed in English. Anyway, I seen an interesting picture of a button on the console next to the seat heater controls. It's also a rocker switch like the heater controls. On the center it has A/T printed on it. The front end of the switch says POWER, and the back end says SNOW. I assume the car is an automatic because the picture does not include the shifter. The mag is dedicated to the all new 2003 Fairlady Z printed a couple years ago. Hmmm, wonder what that control/switch is all about?

TCS settings would be my guess.

differential settings?