Thats definitely surface rust, not paint, it doesnt look dark enough to be rusted through though thats why i say surface rust. Maybe it was sanded for repaint or something and sat out without paint, but i do see some specs of green.
The m100 trailer i was talking about in 4wdtoyowners looks like the bantam trailer in the start of this thread. I'd like to either do some work to the m416 that my folks have or get another m100/m416 to fiddle with, as i may be giving up the Taco for an XJ soon and could use some sort of a bed sometimes.