Many thousands mint or used from A-Z to 1940, virtually all spaces filled incl. U.S. with back of the book spaces full, occasional extra item incl. Germany Air Zepp sets (South America set reprints), decades to put this collection together, rarely seen this complete, value throughout the collection, fresh overall, generally Fine to Very Fine. Estimate $6,000-8,000.
UPDATE: The collection sold for $18,100, including buyer's premium (thanks to Houghton Grandmal for this information). This works out to around fifty cents a stamp.