Paperwork is the 1st thing to look at, e.g. registration
Then there is the serial number or ID tags on the trailer. Is there anything on the closet door, body or tongue? Where was it made? Pictures of various features help those experienced suggest ranges.
The one sure tell item for any boler
is a flat roof.
Sometimes you can tell from the equipment; axle
, stove, fridge
... they all may have dates on them. Literature in the cupboards.
Labels, decals, lights
may even give clues. Cushion fabric if original.