Collect because you like to and not because of an investment. There is absolute surplus of duck stamps and regular stamps too. All the states issuing duck stamps also created some havoc in the marketplace.
Real old ducks stamps unsigned and in very good condition have value, especially if they were handed to you.
There is one or two stamp buyers left in the Twin Cities. I will tell you what one gentleman told me: Every week we get a person or couple who come in with grandpa’s or dad’s stamp collection. The supply greatly exceeds what is left of demand since kids tend not to collect … Stamps issued in the 50s – 80s have no collector value and their small valuations create a situation where they sell for a fraction of face value.
If you want to purchase ducks stamps. There are some large broker-dealers and to be honest .. EBAY is a great place to look and buy. Probably where collectors get something better than selling to a dealer. Or dealers themselves selling online.