Stamp auction catalogs in particular often contain descriptions for items that mention “ex-Green, ex-Burrus” and other former owners of a particular item.
Some collectors attribute extra value to an item if it was owned by a famous philatelist. There have been many over the years. Names like Ferrari, Caspary, Green, Hind, Burrus, to mention just a few.
Being owned by a former philatelist gives the item some degree of authenticity. Kind of a, “If person X owned this item and thought it was genuine, it must be so.”
Franklin Delano Roosevelt collected stamps and was commonly known as the Stamp Collecting President. When FDR died and his collection was sold, even common, inexpensive stamps sold for several dollars or more. Everyone wanted a piece of the president’s collection. Everyone wanted a stamp that passed through FDRs hands. There were thousands of such stamps. Even today, you can still find items for sale that came from the FDR estate. Such items are not rare.
The key to buying stamps like this is being able to prove its lineage. Back in the 1930s and 1940s, not all auction lots were photographed. Sure, there are some unique items that can easily be attributed to a particular collector. But if you have a copy of US Scott #1, how do you know if it was once in the Arthur Hind collection? Proving the lineage of items like this is not always easy. And in some cases, it may not be possible.
Before you spend extra money for a stamp with a pedigree, make sure the pedigree is certain. Don’t let someone tell you, “Oh, this item is ex-Ashbrook.” Your response should be, “Show me the paperwork that proves that.” If it’s in an auction catalog or there is some paperwork proving that a stamp was once owned by a famous philatelist, you can be pretty sure it’s genuine. Just don’t take some else’s word for it.