Check with your states Dept of Motor Vehicles or who ever takes care of titles and registration
in your state. Most have a provision for generating a new VIN
when the paperwork is in order. In CA they have a metal stick-on tag that will have the new number.
Amerigo's predate the 17 digit VIN
system that started in 1981, and the serial number is proprietary to the builders. In as much as they are gone it's of little value for information.
There was only a single model of the molded fiberglass FG-16 Amerigo trailer but, over the years, Amerigo also built a wide range of other trailers and slide in campers. In addition there are several other names associated with building them including Amerigo, Gardner and even KOA, depending on when (rather than where) it was built. The FG-16 literature I have is branded as it being built by Gardner, a KOA company. Gardner folded up his tent years ago and I doubt if, in 2014, that KOA even knows that they were once in that business.