Unknown 120v cord in bay

[riverofcode]

I was doing some tinkering as I make fixes and upgrades to the new toy this weekend and noticed something I had missed before. In the shore cable bay there is a 120v socket which I saw before but there is also a cord with a normal 3 prong plug on it dangling in the back of the bay that someone had wrapped masking tape around. Would I assume this may be a block heater and the outlet I noticed is where you'd plug it in?

Almost forgot... this is in my 2008 TM T40c.
Scott