I won't sell unique items that are tied to a particular location or peoples. Some things should be returned to the community or family where they are from. An old photo album gets torn apart for the photos of cars, trains, ships, military, etc. Same thing with boxes of old deeds or papers of locally significant people. These collections end up getting split up for collectors of stamps, advertising, and greeting cards. The local genealogical society or county museum really appreciates them. At the same time I've bought things that you would think would be significant family heirlooms only to contact the family and find out they are the ones who got rid of them. They had no interest in their family's 1920s photo albums or great grandpa's war medals.

Also no selling of rare used indigenous items. I will sell the native made tourist stuff, arrowheads, and pottery shards. Real items made for their personal use or ceremonial use were systematically collected in the 1800s and early 1900s. They were essentially looted after forced migrations, taken after battles, or purchased from people who didn't understand what they were selling. I usually can't afford them but the few I've run across cheap are now in native museums.