How to tell if trailer is cold rated???

Mine has dual pane windows, heated tanks, enclosed tank valves, even some of the floor is heated, but don't know if it is "cold rated", though we did camp out this past thanksgiving and temps dipped to 4 below with windchill of -10....everything worked fine and we stayed warm. I think some think they have 4 seasons 5er's, and they don't, and some think they don't have one and actually may have one....unless otherwise designated as such, might be hard to tell sometimes.