Hard to say W/O actually seeing it. Are you close by?
Have you gone through this post: viewtopic.php?f=2&t=6192
Being it's located close to the ocean, rust comes to mind. Condition of the top and the screens are worth looking over. That is really low mileage though!
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2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer