If you strip the clear coat and polish your trailer, you will be able to smooth out the finish and get rid of the haze. I know, it's pretty drastic...but....it'll work.
Besides, if you were to replace the panel, it too wouldn't match either and you'd be headed for polishing anyways.
What it looks like, is a previous owner wanted to get rid of older numbers and used something to get them off which stripped the clearcoat. Since then it has oxidized where the clearcoat is missing and not where it is still somewhat intact. Our '64 had a whole bunch of various stages of oxidation prior to our polishing it...it kinda had a neat effect in the right light, but we had
to polish...it's part of the disease!