I have been organizing a seemingly large U.S. stamp collection
inherited by a friend. As an amateur to this so far I have done spread sheets listing stamps by date, name, face value, Scott # & Scott value. Many are new sheets of stamps from the sixties through 2005, postcards & envelopes. There are over 300 first day covers I haven't started on yet. Most recently I've encountered things from The Postal Commemorative Society & am realizing they are difficult to value. Most recently I am stymied by 24 Official First Day covers with descriptive cardboard pages from different countries relating to the July 29th 1981 Wedding of H.R.H The Prince of Wales. Can anyone offer suggestions as to valuing these?