Hilltop camping trailers were manufactured by Hillco, Inc. located at 123 S. Shoop Ave, Wauseon, Ohio. Hillco manufactured boat trailers since at least the 1950's. My best guest is Hillco entered the camping trailer market in 1965, maybe 1964, and continued until 1978. They added travel trailers to their product line as well.
That is about all I know about this manufacturer at this time.