It seems that my vintage travel trailer is not really what it had been claimed to be. I was searching the internet yesterday and came across the website owned by the son of one of the owners of Semaphore Industries. There he posted that what I have is actually a Caboose Travel Trailer built by American Leisure Time Industries, a prototype of what would become the Semaphore Caboose, and as such, there were even fewer of these made, perhaps 10 or less.The full story can be found on his website.
The link he provided to the Life magazine article from August 1970 has just a short caption under the photo of the caboose, stating the travel trailer slept from 6 to 11 depending on which of 3 floor plans you had, and the original purchase price was $5400.
Life Magazine article
Patent filed in August 1970