Tony,
I can just see, from your image, the stamped serial number adjacent to the 'FMC' cast letters. Being a Ford, the serial may be something like 'JTXX', the last two being numerals. It seems to end in '2', but if you clear the paint off, it should become clearer. GMH appear to have stamped the actual ARN onto their plate, but Ford used their own production serial. 'JT' stands for 'Jeep Trailer', by the way!
The comment about desert yellow is right: far toooo late for an authentic restoration, but it's your trailer.
Mike C