Truck camper?
Typically when you hear truck camper one thinks of a camper that sits/slides into the back of a truck. If that is the case, typically no VIN since that type of camper becomes "cargo" of the truck and does not require a separate plate and registration. The truck plate is attached to the slide in camper if it overhangs or blocks the plate location.
Now if you mean a trailer which is pulled by a vehicle via a "bumper hitch" those are a Travel Trailer (AKA TT or Bumper pull trailer) and the trailer has a "tongue or A frame hitch".
TTs that old do not have a "VIN", they have a "Serial Number", that number is often stamped into the trailer tongue "A Frame" and typically on the drivers side top or side of the tongue. Some may not have had anything on the A frame hitch, it may have been a sticky label attached to the drivers side of the trailer box nearest to the trailer tongue. Those labels typically faded or peeled off over the years. The last possible place I can think of is a serial number stamped into the axles or a aluminum band attached to the axles. Serial numbers back then were only placed on the outside of the trailer.
The problem with old "gifted" trailers is the title is often lost, bad (never transferred to the next owner) and no serial number exists anywhere on the trailer.. This often results in a lot of hassle to near impossible to make it road worthy with a plate and registration depending on the State you are living in (which is why folks tend to "gift" them).
The plates near the door are often not much more than certifications with RV manufacturers association and or plumbing/electrical certifications.
Depending on your States DMV, you might be able to apply for a lost title (the folks that gifted it to you may need to do that), you might have to try for a rebuilt title or perhaps a new construction custom built trailer (you lose the original manufacturer date and name). Each avenue will have considerable amount of paperwork, hassles and cost which is why we come back to why it was "gifted" to you.
Be very careful of any out of state "process" which promises a title, that is title washing and your state may reject some titles from known vendors from known states that offer that service.
I wish you well on this venture..
