I've made many trades and when I consider a trade for a vintage era card (anything pre-80s, more likely pre-70s) I try to inform my trade partner of any condition issues. Some people like me will take a lesser grade for a higher grade card when appropriate. It's all dependent on the partnership. I haven't had anyone complain about condition to me, nor have I of others as most of the time everyone seems willing to provide whatever information is required to complete a trade.
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“Aslan didn't tell Pole what would happen. He only told her what to do. That fellow will be the death of us once he's up, I shouldn't wonder. But that doesn't let us off following the signs.” - Puddleglum in The Silver Chair by C. S. Lewis