Collection of 4 Vintage 1960s US Postage Stamp First Day Covers FDC on Decorative Envelopes

Collection of four vintage 1960s US Postage First Day Cover (FDC) stamp and envelope sets.
- 1966 5 cent US stamp commemorates the 50 year anniversary of the Migratory Bird Treaty between the USA and Canada, established in 1916.  
- 1968 6 cent US stamp featuring the US flag and White House
- 1699 5 cent US stamp featuring the US flag and the White House
- 4 cent US stamp commemorating the 1962 World's Fair in Seattle, Washington, featuring the Space Needle
Envelopes measures aprox. 6.5" x 3.5".