Yup. That is the breaker to protect the 12v distribution. 12V from TV and Battery on one side and 12v distribution on the other. Usually auto reset though. Had to replace the one on my 2005 Wolf Pack. It was a rusty mess. Thanks for the pic. Looks like they picked off power for the jack and maybe input from the solar plug.
2005 Wolf Pack WP22-2016 Grey Wolf 26RR-Gone
2004 Siverado 2500HD Duramax
2013 Keystone Springdale 5r
1998 Honda Valkerie
2016 Camping 148 days so far
Trailers I have had have a push/pull usually silver in color....either next to battery box or on main panel inside trailer....and is never labeled LOL....if tow vehicle and shore power are both unhooked....turn on trailer lights and push pull switch to see how it works.....one way lights burn, other way they don t....