Almost everything that has been done to a piece of cinema paper — tape, backing, repair, trimming — is visible from behind and invisible from the front.
Ask for the reverse
It is the request that separates a careful buyer from a hopeful one. Tape stains, paper repairs, linen or paper backing and old mounting all show there.
Then ask for a measurement
Formats vary by era and studio, so ask for the sheet measured in centimetres on camera. A piece that has been trimmed measures short, and a trimmed poster is a different object from an untrimmed one.
Then ask the printing question
"Is this an original release printing, a reissue, or a reproduction?"
A good seller answers directly and tells you how confident they are. A seller who will not answer has told you something. Reproductions are perfectly sellable when they are described as reproductions — the problem is only ever silence.
Autographs and props are provenance items
No video call authenticates a signature. What you can ask for is history: who got it, when, where, and what came with it. A certificate is worth exactly as much as the reputation of whoever issued it, and no more.
If the signature is the reason you are bidding, bid as though the price has to survive the possibility that it cannot ever be confirmed.
What protection covers
A reproduction sold as an original, a backed poster sold as unbacked, a trimmed sheet sold as full size — all not-as-described. Buyer protection runs for seven days from delivery.
It does not cover a signature you accepted on trust and now doubt. That is why the questions above are worth asking before you bid rather than after.
Questions people ask
Does linen-backing reduce the value?
It changes what the piece is. Many collectors accept or prefer it for large pieces. Undeclared, it is a dispute.
Are fold lines a defect?
Not if the poster was issued folded. Separation at the folds is. Ask which you are looking at.
Should I buy a poster that has been trimmed?
At a trimmed price, if you want the image. Never at a full-size price.