My '84 originally had the same material for the cushion covers. I have rounded windows on mineand I had original round taillights (I have replaced mine with round LEDs in the same size) but I do not have the "flat" rear window - I wish I did, as I would LOVE another sliding window there. You can replace the roof vent if you aren't afraid to cut a hole, Scamp sells replacements.
My door is lined with plain tan/off-white vinyl, with the "elephant hide" ensolite throughout the rest.
I think based on everything you can narrow down age to '84-85 as suggested, beyond that it's not terribly critical - it's still a 30 year old trailer no matter it's exact birthday