Greetings 1stairstream!
There is a value in virtually any Vintage Airstream, but that value is tempered by condition and to a lesser extent the region of the country where that trailer is located. One of the most frequently mentioned guides to value determination for Vintage Airstreams is the
Price vs. Condition guide. The photos posted do indicate that it is a
1966 through
1968 Overlander International.
There is one unique item on the 1966-1968 Airstreams that can pose difficulties in restoration, and that is the Corning Tempered Glass Windows. Should any of the windows be missing or have Plexiglass or Lexan replacements, the costs can escalate quickly. The situation is better today than it was a few years ago when the only source for replacement window glass for a 1966-1968 Airstream was from a salvaged trailer; today, reproductions are available from several sources. Other than the Corning Tempered Glass Windows and their unique operators/latches, the balance of the 1966-1968 trailers are typical Airstream construction.
In addition to the Price vs. Condition guide, the Volunteer Inspectors' Checklist mentioned on the Airforums home page can also help you to assess the trailer . . . there also may be a volunteer inspector located near the trailer who could help you assess the trailer.
The biggest issue revealed by the photos is that the Plasticoat has failed and is particularly bad on the endcaps and upper body panels . . . something that is quite common on "as-found" Vintage Airstreams. Another item of concern is that the LP tanks are missing. Missing tanks aren't a huge problem, but if you want Worthington Aluminum LP tanks that can be polished to match your Airstream, the cost for replacements can approach $500 depending upon size of tank chosen (I purchased 40 pound tanks for my Overlander rather than the more "standard" 30 pound tanks for greater travel time between refills).
Good luck with your investigation.
Kevin