Hello Newt, you could contact the Russell Military Museum, they are located right on the Illinois/ Wisconsin border at I-94 their contact info is:
Phone (847) 395-7020
43363 Old Highway 41
Russell, IL 60075
Alternately, you can try: Chicago Area And Northern Illinois Military Vehicle Collectors Club
Hank LaBarbara at: Hank@dukw.com
Between them, you should be able to find the information you are looking for.
Thank you tankgeezer, I will do that!
I am waiting on replies from the two mentioned above and was told to add Hayes Otoupalik, specialist in American military artifacts: email@example.com to the list.
Well, it seems I need to pay an appraiser, the IRS prevents the museums from putting a value on it. They did confirm that it was an Army Trailer.
You might sign up on the Military Vehicle collectors site, and maybe one of their number can give you a value for it.