Ask on the listing before the show. Public questions stay for the next buyer, and in this category the same questions come up every time.
The questions
"Can you show the reverse?" Tape, backing, repairs and old mounting all live there and none of it faces the front. The single most useful request in the category. Non-answer: a better photo of the image.
"Can you measure the sheet in centimetres?" Formats vary by era and studio, so the measurement is the fact. A trimmed poster measures short.
"Original printing, reissue, or reproduction — and how do you know?" All three are legitimate to sell. Only silence is a problem.
"Has it been linen-backed, trimmed, retouched or repaired?" All normal, all to be declared. Good restoration is designed not to show.
"Was it issued folded?" Fold lines are not damage if the sheet was issued folded. Separation at the folds is. Ask which you are looking at.
For signed pieces
"What do you know about the signature?" A provenance question, not a condition one, and no video call settles it. Provenance.
What protection covers
A reproduction sold as original, a backed poster sold as unbacked, a trimmed sheet sold as full size: seven days from delivery.
Questions people ask
Does linen backing reduce value?
It changes what the piece is. Many collectors accept or prefer it on large sheets. Undeclared, it is a dispute.
Should I buy a reproduction?
At reproduction prices, if you want the image.
How will it be sent?
Ask. Rolled stays rolled, folded stays folded. Delivering posters.