When I was in High School, my uncle owned a [b]Marlette of about that size. It was built in the early 60's and was a "park" model (no water tanks, regular toilet). That company also built larger "Mobile Homes".
I thought about that trailer, and searched old photo albums. I found it!
True, it is not fiberglass.
But it was considered a "high quality" brand name of it's day. Uncle Hoddy's Marlette
was maybe 30' long and 8' wide.