for sure the door and windows
are much more recent additions. Those were not being sold
in the 1970's
As far as I know the last year the Campsters were made was 1971. The company that owned the Trailswest Campster
company did not mold the shells, or make even the steel frames that went under the trailer. They contracted with other companies to do that part of the production work. Of course they also did not make the windows
and doors. They were pretty much a final assembly only operation in their Oregon facility.
There could have been a stockpile of shells already made when Trailswest Campster went out of business that might then have been sold
off to another business.
I would suspect that the company that did the actual molding was the company that ended up with actual ownership of the molds after the Trailswest Campster company dissolved. It would not be unusual for a company that goes out of business to still owe money to a sub contractor. The company that made the shells would have then had the right to make and sell the shells to other companies.