IMHO, its all about condition and without pictures, its hard to tell. Even with pictures, soft floor, leaks
, appliances not all working, there are lots of variables. One person's very good is another person's mediocre, and a third person's excellent.
I can tell you, I've looked at a lot of vintage FG trailers recently all described as excellent, and on a sliding scale I would call them anything from poor with serious damage to good but needing updates and not everything works.
Stored indoors or stored outside?
IMHO, rarity doesn't matter. Buyer will not be a collector. I could see prices from about $2500 to $7500. Guess on my part!