risking their professional relationships, and could also ruin your standing among dealers, thereby adversely affecting your ability to buy works
Do: Request a condition report
You can request a condition report from any gallery, auction house, or directly from an art dealer.
Particularly for historical works which belong to the "secondary market"
Although there isn't a universal model for reports on condition, there are some general standards. A diagram of an example is provided in a lot of condition reports.
The artwork is accompanied by notes of any marks, scratches, knicks, or tears. Here's an example of a condition report from Georgia O'Keeffe.
Depending on the price of the item, it may make sense to hire a neutral third party to prepare the condition report.
You will probably pay for the service.
Art collectors with an Artwork Archive Premier Collector plan can digitally store the condition reports for their art pieces using the "additional files"
Don't assume that the work is authenticated by the artist.