Newbie Questions: Mystery Switch and Inverter?

[tpellegrini]

We took our new Vengeance 320A out for the first time last week and had no issues. (Yay!) However I still have two mysteries to solve. Above my tanks/battery panel near all the other switches there is a 12v lighted switch the dealer couldn't identify, and neither can I. I suspect it might be for the tank heater but I'm hoping someone here knows for sure. Secondly, while going through the manuals I was provided I found one for an inverter. That's great if it's there but I'm not aware I have one. I haven't seen it, and I'm not aware any AC outlets work on battery. Where might it be installed and for which circuits?

Thanks!