I though you guys might like these links to pages on the excellent German OldieCaravan.de
web site of 1950s and 1960s 'caravans' (travel trailers) that show fiberglass models (just guessed-at from their appearance). 'Hybrid' refers to part-sticky trailers like the Eriba and some makes have mixes of sticky and molded bodies.
Rather than waste bandwidth on photos of all of them, attached are a couple of nice examples, the stylish Fahti and the odd (apparently all-molded but in many pieces) Intercamp.
Constructam (not all fg)
MKP (not all fg)