Unknown Broken Part - Help!

[turkish6]

So I was at the boat today..
I removed the box. I connected "+" to "+", "-" to "-" and ground to ground. Flipped on the shore power and everything worked fine. My batter charger came on and started charging and after about an 1.5 hours it shut off when the batteries were full. So I am assuming the previous owner used this for the inverter that was installed. Either way I don't see any problems with removing the box. Thanks for the help everyone.

[Microship]

Ah, I love happy endings! Good to be rid of a mystery box, too...